[PATCH v3 7/7] KVM: arm64: Normalize cache configuration
From: Akihiko Odaki
Date: Sun Dec 18 2022 - 00:16:48 EST
Before this change, the cache configuration of the physical CPU was
exposed to vcpus. This is problematic because the cache configuration a
vcpu sees varies when it migrates between vcpus with different cache
configurations.
Fabricate cache configuration from the sanitized value, which holds the
CTR_EL0 value the userspace sees regardless of which physical CPU it
resides on.
CLIDR_EL1 is now writable from the userspace so that the VMM can
restore the values saved with the old kernel.
Suggested-by: Marc Zyngier <maz@xxxxxxxxxx>
Signed-off-by: Akihiko Odaki <akihiko.odaki@xxxxxxxxxx>
---
arch/arm64/include/asm/cache.h | 3 +
arch/arm64/include/asm/kvm_host.h | 1 +
arch/arm64/kvm/sys_regs.c | 183 +++++++++++++++---------------
3 files changed, 96 insertions(+), 91 deletions(-)
diff --git a/arch/arm64/include/asm/cache.h b/arch/arm64/include/asm/cache.h
index ab7133654a72..a51e6e8f3171 100644
--- a/arch/arm64/include/asm/cache.h
+++ b/arch/arm64/include/asm/cache.h
@@ -22,6 +22,9 @@
#define CLIDR_CTYPE(clidr, level) \
(((clidr) & CLIDR_CTYPE_MASK(level)) >> CLIDR_CTYPE_SHIFT(level))
+/* Ttypen, bits [2(n - 1) + 34 : 2(n - 1) + 33], for n = 1 to 7 */
+#define CLIDR_TTYPE_SHIFT(level) (2 * ((level) - 1) + CLIDR_EL1_Ttypen_SHIFT)
+
/*
* Memory returned by kmalloc() may be used for DMA, so we must make
* sure that all such allocations are cache aligned. Otherwise,
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index cfc6930efe1b..27abf81c6910 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -178,6 +178,7 @@ struct kvm_vcpu_fault_info {
enum vcpu_sysreg {
__INVALID_SYSREG__, /* 0 is reserved as an invalid value */
MPIDR_EL1, /* MultiProcessor Affinity Register */
+ CLIDR_EL1, /* Cache Level ID Register */
CSSELR_EL1, /* Cache Size Selection Register */
SCTLR_EL1, /* System Control Register */
ACTLR_EL1, /* Auxiliary Control Register */
diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
index a7199f34e321..9fd0b28e29bd 100644
--- a/arch/arm64/kvm/sys_regs.c
+++ b/arch/arm64/kvm/sys_regs.c
@@ -11,6 +11,7 @@
#include <linux/bitfield.h>
#include <linux/bsearch.h>
+#include <linux/cacheinfo.h>
#include <linux/kvm_host.h>
#include <linux/mm.h>
#include <linux/printk.h>
@@ -81,9 +82,6 @@ void vcpu_write_sys_reg(struct kvm_vcpu *vcpu, u64 val, int reg)
__vcpu_sys_reg(vcpu, reg) = val;
}
-/* 3 bits per cache level, as per CLIDR, but non-existent caches always 0 */
-static u32 cache_levels;
-
/* CSSELR values; used to index KVM_REG_ARM_DEMUX_ID_CCSIDR */
#define CSSELR_MAX 14
@@ -101,47 +99,36 @@ static u8 get_min_cache_line_size(u32 csselr)
/* Which cache CCSIDR represents depends on CSSELR value. */
static u32 get_ccsidr(struct kvm_vcpu *vcpu, u32 csselr)
{
- u32 ccsidr_index = csselr & (CSSELR_EL1_Level | CSSELR_EL1_InD);
- u32 ccsidr;
-
- if (vcpu->arch.ccsidr && is_valid_cache(ccsidr_index) &&
- !(kvm_has_mte(vcpu->kvm) && (csselr & CSSELR_EL1_TnD)))
- return vcpu->arch.ccsidr[ccsidr_index];
-
- /* Make sure noone else changes CSSELR during this! */
- local_irq_disable();
- write_sysreg(csselr, csselr_el1);
- isb();
- ccsidr = read_sysreg(ccsidr_el1);
- local_irq_enable();
-
- return ccsidr;
-}
-
-static bool is_valid_cache(u32 val)
-{
- u32 level, ctype;
+ u64 ctr_el0;
+ int field;
- if (val >= CSSELR_MAX)
- return false;
+ if (vcpu->arch.ccsidr)
+ return vcpu->arch.ccsidr[csselr];
- /* Bottom bit is Instruction or Data bit. Next 3 bits are level. */
- level = (val >> 1);
- ctype = (cache_levels >> (level * 3)) & 7;
+ ctr_el0 = read_sanitised_ftr_reg(SYS_CTR_EL0);
+ field = csselr & CSSELR_EL1_InD ? CTR_EL0_IminLine_SHIFT : CTR_EL0_DminLine_SHIFT;
- switch (ctype) {
- case 0: /* No cache */
- return false;
- case 1: /* Instruction cache only */
- return (val & 1);
- case 2: /* Data cache only */
- case 4: /* Unified cache */
- return !(val & 1);
- case 3: /* Separate instruction and data caches */
- return true;
- default: /* Reserved: we can't know instruction or data. */
- return false;
- }
+ /*
+ * Fabricate a CCSIDR value as the overriding value does not exist.
+ * The real CCSIDR value will not be used as it can vary by the
+ * physical CPU which the vcpu currently resides in.
+ *
+ * The line size is determined with arm64_ftr_reg_ctrel0.sys_val, which
+ * should be valid for all CPUs even if they have different cache
+ * configuration.
+ *
+ * The associativity bits are cleared, meaning the geometry of all data
+ * and unified caches (which are guaranteed to be PIPT and thus
+ * non-aliasing) are 1 set and 1 way.
+ * Guests should not be doing cache operations by set/way at all, and
+ * for this reason, we trap them and attempt to infer the intent, so
+ * that we can flush the entire guest's address space at the appropriate
+ * time. The exposed geometry minimizes the number of the traps.
+ * [If guests should attempt to infer aliasing properties from the
+ * geometry (which is not permitted by the architecture), they would
+ * only do so for virtually indexed caches.]
+ */
+ return get_min_cache_line_size(csselr) << CCSIDR_EL1_LineSize_SHIFT;
}
static int set_ccsidr(struct kvm_vcpu *vcpu, u32 csselr, u32 val)
@@ -162,8 +149,7 @@ static int set_ccsidr(struct kvm_vcpu *vcpu, u32 csselr, u32 val)
return -ENOMEM;
for (i = 0; i < CSSELR_MAX; i++)
- if (is_valid_cache(i))
- ccsidr[i] = get_ccsidr(vcpu, i);
+ ccsidr[i] = get_ccsidr(vcpu, i);
vcpu->arch.ccsidr = ccsidr;
}
@@ -1352,10 +1338,64 @@ static bool access_clidr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
if (p->is_write)
return write_to_read_only(vcpu, p, r);
- p->regval = read_sysreg(clidr_el1);
+ p->regval = __vcpu_sys_reg(vcpu, r->reg);
return true;
}
+/*
+ * Fabricate a CLIDR_EL1 value instead of using the real value, which can vary
+ * by the physical CPU which the vcpu currently resides in.
+ */
+static void reset_clidr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
+{
+ u64 ctr_el0 = read_sanitised_ftr_reg(SYS_CTR_EL0);
+ u64 clidr;
+ u8 loc;
+
+ if ((ctr_el0 & CTR_EL0_IDC) || cpus_have_const_cap(ARM64_HAS_STAGE2_FWB)) {
+ /*
+ * Data cache clean to the PoU is not required so LoUU and LoUIS
+ * will not be set and a unified cache, which will be marked as
+ * LoC, will be added.
+ *
+ * If not DIC, let the unified cache L2 so that an instruction
+ * cache can be added as L1 later.
+ */
+ loc = (ctr_el0 & CTR_EL0_DIC) ? 1 : 2;
+ clidr = CACHE_TYPE_UNIFIED << CLIDR_CTYPE_SHIFT(loc);
+ } else {
+ /*
+ * Data cache clean to the PoU is required so let L1 have a data
+ * cache and mark it as LoUU and LoUIS. As L1 has a data cache,
+ * it can be marked as LoC too.
+ */
+ loc = 1;
+ clidr = 1 << CLIDR_LOUU_SHIFT;
+ clidr |= 1 << CLIDR_LOUIS_SHIFT;
+ clidr |= CACHE_TYPE_DATA << CLIDR_CTYPE_SHIFT(1);
+ }
+
+ /*
+ * Instruction cache invalidation to the PoU is required so let L1 have
+ * an instruction cache. If L1 already has a data cache, it will be
+ * CACHE_TYPE_SEPARATE.
+ */
+ if (!(ctr_el0 & CTR_EL0_DIC))
+ clidr |= CACHE_TYPE_INST << CLIDR_CTYPE_SHIFT(1);
+
+ clidr |= loc << CLIDR_LOC_SHIFT;
+
+ /*
+ * Add tag cache unified to data cache. Allocation tags and data are
+ * unified in a cache line so that it looks valid even if there is only
+ * one cache line.
+ */
+ if (kvm_has_mte(vcpu->kvm))
+ clidr |= 2 << CLIDR_TTYPE_SHIFT(loc);
+
+ __vcpu_sys_reg(vcpu, r->reg) = clidr;
+}
+
static bool access_csselr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
const struct sys_reg_desc *r)
{
@@ -1377,22 +1417,12 @@ static bool access_ccsidr(struct kvm_vcpu *vcpu, struct sys_reg_params *p,
return write_to_read_only(vcpu, p, r);
csselr = vcpu_read_sys_reg(vcpu, CSSELR_EL1);
+ csselr &= CSSELR_EL1_Level | CSSELR_EL1_InD;
+ if (csselr >= CSSELR_MAX)
+ return undef_access(vcpu, p, r);
+
p->regval = get_ccsidr(vcpu, csselr);
- /*
- * Guests should not be doing cache operations by set/way at all, and
- * for this reason, we trap them and attempt to infer the intent, so
- * that we can flush the entire guest's address space at the appropriate
- * time.
- * To prevent this trapping from causing performance problems, let's
- * expose the geometry of all data and unified caches (which are
- * guaranteed to be PIPT and thus non-aliasing) as 1 set and 1 way.
- * [If guests should attempt to infer aliasing properties from the
- * geometry (which is not permitted by the architecture), they would
- * only do so for virtually indexed caches.]
- */
- if (!(csselr & 1)) // data or unified cache
- p->regval &= ~GENMASK(27, 3);
return true;
}
@@ -1681,7 +1711,7 @@ static const struct sys_reg_desc sys_reg_descs[] = {
{ SYS_DESC(SYS_CNTKCTL_EL1), NULL, reset_val, CNTKCTL_EL1, 0},
{ SYS_DESC(SYS_CCSIDR_EL1), access_ccsidr },
- { SYS_DESC(SYS_CLIDR_EL1), access_clidr },
+ { SYS_DESC(SYS_CLIDR_EL1), access_clidr, reset_clidr, CLIDR_EL1 },
{ SYS_DESC(SYS_CCSIDR2_EL1), undef_access },
{ SYS_DESC(SYS_SMIDR_EL1), undef_access },
{ SYS_DESC(SYS_CSSELR_EL1), access_csselr, reset_unknown, CSSELR_EL1 },
@@ -2693,7 +2723,6 @@ id_to_sys_reg_desc(struct kvm_vcpu *vcpu, u64 id,
FUNCTION_INVARIANT(midr_el1)
FUNCTION_INVARIANT(revidr_el1)
-FUNCTION_INVARIANT(clidr_el1)
FUNCTION_INVARIANT(aidr_el1)
static void get_ctr_el0(struct kvm_vcpu *v, const struct sys_reg_desc *r)
@@ -2705,7 +2734,6 @@ static void get_ctr_el0(struct kvm_vcpu *v, const struct sys_reg_desc *r)
static struct sys_reg_desc invariant_sys_regs[] = {
{ SYS_DESC(SYS_MIDR_EL1), NULL, get_midr_el1 },
{ SYS_DESC(SYS_REVIDR_EL1), NULL, get_revidr_el1 },
- { SYS_DESC(SYS_CLIDR_EL1), NULL, get_clidr_el1 },
{ SYS_DESC(SYS_AIDR_EL1), NULL, get_aidr_el1 },
{ SYS_DESC(SYS_CTR_EL0), NULL, get_ctr_el0 },
};
@@ -2758,7 +2786,7 @@ static int demux_c15_get(struct kvm_vcpu *vcpu, u64 id, void __user *uaddr)
return -ENOENT;
val = (id & KVM_REG_ARM_DEMUX_VAL_MASK)
>> KVM_REG_ARM_DEMUX_VAL_SHIFT;
- if (!is_valid_cache(val))
+ if (val >= CSSELR_MAX)
return -ENOENT;
return put_user(get_ccsidr(vcpu, val), uval);
@@ -2783,7 +2811,7 @@ static int demux_c15_set(struct kvm_vcpu *vcpu, u64 id, void __user *uaddr)
return -ENOENT;
val = (id & KVM_REG_ARM_DEMUX_VAL_MASK)
>> KVM_REG_ARM_DEMUX_VAL_SHIFT;
- if (!is_valid_cache(val))
+ if (val >= CSSELR_MAX)
return -ENOENT;
if (get_user(newval, uval))
@@ -2882,13 +2910,7 @@ int kvm_arm_sys_reg_set_reg(struct kvm_vcpu *vcpu, const struct kvm_one_reg *reg
static unsigned int num_demux_regs(void)
{
- unsigned int i, count = 0;
-
- for (i = 0; i < CSSELR_MAX; i++)
- if (is_valid_cache(i))
- count++;
-
- return count;
+ return CSSELR_MAX;
}
static int write_demux_regids(u64 __user *uindices)
@@ -2898,8 +2920,6 @@ static int write_demux_regids(u64 __user *uindices)
val |= KVM_REG_ARM_DEMUX_ID_CCSIDR;
for (i = 0; i < CSSELR_MAX; i++) {
- if (!is_valid_cache(i))
- continue;
if (put_user(val | i, uindices))
return -EFAULT;
uindices++;
@@ -3001,7 +3021,6 @@ int kvm_sys_reg_table_init(void)
{
bool valid = true;
unsigned int i;
- struct sys_reg_desc clidr;
/* Make sure tables are unique and in order. */
valid &= check_sysreg_table(sys_reg_descs, ARRAY_SIZE(sys_reg_descs), false);
@@ -3018,23 +3037,5 @@ int kvm_sys_reg_table_init(void)
for (i = 0; i < ARRAY_SIZE(invariant_sys_regs); i++)
invariant_sys_regs[i].reset(NULL, &invariant_sys_regs[i]);
- /*
- * CLIDR format is awkward, so clean it up. See ARM B4.1.20:
- *
- * If software reads the Cache Type fields from Ctype1
- * upwards, once it has seen a value of 0b000, no caches
- * exist at further-out levels of the hierarchy. So, for
- * example, if Ctype3 is the first Cache Type field with a
- * value of 0b000, the values of Ctype4 to Ctype7 must be
- * ignored.
- */
- get_clidr_el1(NULL, &clidr); /* Ugly... */
- cache_levels = clidr.val;
- for (i = 0; i < 7; i++)
- if (((cache_levels >> (i*3)) & 7) == 0)
- break;
- /* Clear all higher bits. */
- cache_levels &= (1 << (i*3))-1;
-
return 0;
}
--
2.38.1