RE: [PATCH v6 5/6] Drivers: hv: vmbus: Support TDX guests

[Michael Kelley (LINUX)]

From: Dexuan Cui <decui@xxxxxxxxxxxxx>
> 
> Add Hyper-V specific code so that a TDX guest can run on Hyper-V:
>   No need to use hv_vp_assist_page.
>   Don't use the unsafe Hyper-V TSC page.
>   Don't try to use HV_REGISTER_CRASH_CTL.
>   Don't trust Hyper-V's TLB-flushing hypercalls.
>   Don't use lazy EOI.

Nit:  Actually, you overdid the cleanup. :-(  The line in v5 about
"Share SynIC Event/Message pages" was correct.  It was only the
part about VMBus Monitor pages that no longer applied.

> 
> Signed-off-by: Dexuan Cui <decui@xxxxxxxxxxxxx>
> ---
> 
> Changes in v2:
>   Used a new function hv_set_memory_enc_dec_needed() in
>     __set_memory_enc_pgtable().
>   Added the missing set_memory_encrypted() in hv_synic_free().
> 
> Changes in v3:
>   Use pgprot_decrypted(PAGE_KERNEL)in hv_ringbuffer_init().
>   (Do not use PAGE_KERNEL_NOENC, which doesn't exist for ARM64).
> 
>   Used cc_mkdec() in hv_synic_enable_regs().
> 
>   ms_hyperv_init_platform():
>     Explicitly do not use HV_X64_REMOTE_TLB_FLUSH_RECOMMENDED.
>     Explicitly do not use HV_X64_APIC_ACCESS_RECOMMENDED.
> 
>   Enabled __send_ipi_mask() and __send_ipi_one() for TDX guests.
> 
> Changes in v4:
>   A minor rebase to Michael's v7 DDA patchset. I'm very happy that
>     I can drop my v3 change to arch/x86/mm/pat/set_memory.c due to
>     Michael's work.
> 
> Changes in v5:
>   Added memset() to clear synic_message_page and synic_event_page()
> after set_memory_decrypted().
>   Rebased the patch since "post_msg_page" has been removed in
> hyperv-next.
>   Improved the error handling in hv_synic_alloc()/free() [Michael
> Kelley]
> 
> Changes in v6:
>   Adressed Michael Kelley's comments on patch 5:
>     Removed 2 unnecessary lines of messages from the commit log.
>     Fixed the error handling path for hv_synic_alloc()/free().
>     Printed the 'ret' in hv_synic_alloc()/free().
> 
>  arch/x86/hyperv/hv_apic.c      |  6 ++--
>  arch/x86/hyperv/hv_init.c      | 19 +++++++---
>  arch/x86/kernel/cpu/mshyperv.c | 21 ++++++++++-
>  drivers/hv/hv.c                | 65 ++++++++++++++++++++++++++++++++--
>  4 files changed, 101 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/x86/hyperv/hv_apic.c b/arch/x86/hyperv/hv_apic.c
> index 1fbda2f94184..b28da8b41b45 100644
> --- a/arch/x86/hyperv/hv_apic.c
> +++ b/arch/x86/hyperv/hv_apic.c
> @@ -177,7 +177,8 @@ static bool __send_ipi_mask(const struct cpumask *mask, int
> vector,
>  	    (exclude_self && weight == 1 && cpumask_test_cpu(this_cpu, mask)))
>  		return true;
> 
> -	if (!hv_hypercall_pg)
> +	/* A TDX guest doesn't use hv_hypercall_pg. */
> +	if (!hv_isolation_type_tdx() && !hv_hypercall_pg)
>  		return false;
> 
>  	if ((vector < HV_IPI_LOW_VECTOR) || (vector > HV_IPI_HIGH_VECTOR))
> @@ -231,7 +232,8 @@ static bool __send_ipi_one(int cpu, int vector)
> 
>  	trace_hyperv_send_ipi_one(cpu, vector);
> 
> -	if (!hv_hypercall_pg || (vp == VP_INVAL))
> +	/* A TDX guest doesn't use hv_hypercall_pg. */
> +	if ((!hv_isolation_type_tdx() && !hv_hypercall_pg) || (vp == VP_INVAL))
>  		return false;
> 
>  	if ((vector < HV_IPI_LOW_VECTOR) || (vector > HV_IPI_HIGH_VECTOR))
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index f175e0de821c..f28357ecad7d 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -79,7 +79,7 @@ static int hyperv_init_ghcb(void)
>  static int hv_cpu_init(unsigned int cpu)
>  {
>  	union hv_vp_assist_msr_contents msr = { 0 };
> -	struct hv_vp_assist_page **hvp = &hv_vp_assist_page[cpu];
> +	struct hv_vp_assist_page **hvp;
>  	int ret;
> 
>  	ret = hv_common_cpu_init(cpu);
> @@ -89,6 +89,7 @@ static int hv_cpu_init(unsigned int cpu)
>  	if (!hv_vp_assist_page)
>  		return 0;
> 
> +	hvp = &hv_vp_assist_page[cpu];
>  	if (hv_root_partition) {
>  		/*
>  		 * For root partition we get the hypervisor provided VP assist
> @@ -398,11 +399,21 @@ void __init hyperv_init(void)
>  	if (hv_common_init())
>  		return;
> 
> -	hv_vp_assist_page = kcalloc(num_possible_cpus(),
> -				    sizeof(*hv_vp_assist_page), GFP_KERNEL);
> +	/*
> +	 * The VP assist page is useless to a TDX guest: the only use we
> +	 * would have for it is lazy EOI, which can not be used with TDX.
> +	 */
> +	if (hv_isolation_type_tdx())
> +		hv_vp_assist_page = NULL;
> +	else
> +		hv_vp_assist_page = kcalloc(num_possible_cpus(),
> +					    sizeof(*hv_vp_assist_page),
> +					    GFP_KERNEL);
>  	if (!hv_vp_assist_page) {
>  		ms_hyperv.hints &= ~HV_X64_ENLIGHTENED_VMCS_RECOMMENDED;
> -		goto common_free;
> +
> +		if (!hv_isolation_type_tdx())
> +			goto common_free;
>  	}
> 
>  	if (hv_isolation_type_snp()) {
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index 2fd687a80033..b95b689efa07 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -404,8 +404,27 @@ static void __init ms_hyperv_init_platform(void)
> 
>  		if (hv_get_isolation_type() == HV_ISOLATION_TYPE_SNP)
>  			static_branch_enable(&isolation_type_snp);
> -		else if (hv_get_isolation_type() == HV_ISOLATION_TYPE_TDX)
> +		else if (hv_get_isolation_type() == HV_ISOLATION_TYPE_TDX) {
>  			static_branch_enable(&isolation_type_tdx);
> +
> +			/*
> +			 * The GPAs of SynIC Event/Message pages and VMBus
> +			 * Moniter pages need to be added by this offset.
> +			 */
> +			ms_hyperv.shared_gpa_boundary = cc_mkdec(0);
> +
> +			/* Don't use the unsafe Hyper-V TSC page */
> +			ms_hyperv.features &= ~HV_MSR_REFERENCE_TSC_AVAILABLE;
> +
> +			/* HV_REGISTER_CRASH_CTL is unsupported */
> +			ms_hyperv.misc_features &= ~HV_FEATURE_GUEST_CRASH_MSR_AVAILABLE;
> +
> +			/* Don't trust Hyper-V's TLB-flushing hypercalls */
> +			ms_hyperv.hints &= ~HV_X64_REMOTE_TLB_FLUSH_RECOMMENDED;
> +
> +			/* A TDX VM must use x2APIC and doesn't use lazy EOI */
> +			ms_hyperv.hints &= ~HV_X64_APIC_ACCESS_RECOMMENDED;
> +		}
>  	}
> 
>  	if (hv_max_functions_eax >= HYPERV_CPUID_NESTED_FEATURES) {
> diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c
> index de6708dbe0df..af959e87b6e7 100644
> --- a/drivers/hv/hv.c
> +++ b/drivers/hv/hv.c
> @@ -18,6 +18,7 @@
>  #include <linux/clockchips.h>
>  #include <linux/delay.h>
>  #include <linux/interrupt.h>
> +#include <linux/set_memory.h>
>  #include <clocksource/hyperv_timer.h>
>  #include <asm/mshyperv.h>
>  #include "hyperv_vmbus.h"
> @@ -80,6 +81,7 @@ int hv_synic_alloc(void)
>  {
>  	int cpu;
>  	struct hv_per_cpu_context *hv_cpu;
> +	int ret = -ENOMEM;
> 
>  	/*
>  	 * First, zero all per-cpu memory areas so hv_synic_free() can
> @@ -120,9 +122,42 @@ int hv_synic_alloc(void)
>  				(void *)get_zeroed_page(GFP_ATOMIC);
>  			if (hv_cpu->synic_event_page == NULL) {
>  				pr_err("Unable to allocate SYNIC event page\n");
> +
> +				free_page((unsigned long)hv_cpu->synic_message_page);
> +				hv_cpu->synic_message_page = NULL;
> +
>  				goto err;
>  			}
>  		}
> +
> +		/* It's better to leak the page if the decryption fails. */
> +		if (hv_isolation_type_tdx()) {
> +			ret = set_memory_decrypted(
> +				(unsigned long)hv_cpu->synic_message_page, 1);
> +			if (ret) {
> +				pr_err("Failed to decrypt SYNIC msg page: %d\n", ret);
> +				hv_cpu->synic_message_page = NULL;
> +
> +				/*
> +				 * Free the event page so that a TDX VM won't
> +				 * try to encrypt the page in hv_synic_free().
> +				 */
> +				free_page((unsigned long)hv_cpu->synic_event_page);
> +				hv_cpu->synic_event_page = NULL;
> +				goto err;
> +			}
> +
> +			ret = set_memory_decrypted(
> +				(unsigned long)hv_cpu->synic_event_page, 1);
> +			if (ret) {
> +				pr_err("Failed to decrypt SYNIC event page: %d\n", ret);
> +				hv_cpu->synic_event_page = NULL;
> +				goto err;
> +			}
> +
> +			memset(hv_cpu->synic_message_page, 0, PAGE_SIZE);
> +			memset(hv_cpu->synic_event_page, 0, PAGE_SIZE);
> +		}
>  	}
> 
>  	return 0;
> @@ -131,18 +166,40 @@ int hv_synic_alloc(void)
>  	 * Any memory allocations that succeeded will be freed when
>  	 * the caller cleans up by calling hv_synic_free()
>  	 */
> -	return -ENOMEM;
> +	return ret;
>  }
> 
> 
>  void hv_synic_free(void)
>  {
>  	int cpu;
> +	int ret;
> 
>  	for_each_present_cpu(cpu) {
>  		struct hv_per_cpu_context *hv_cpu
>  			= per_cpu_ptr(hv_context.cpu_context, cpu);
> 
> +		/* It's better to leak the page if the encryption fails. */
> +		if (hv_isolation_type_tdx()) {
> +			if (hv_cpu->synic_message_page) {
> +				ret = set_memory_encrypted((unsigned long)
> +					hv_cpu->synic_message_page, 1);
> +				if (ret) {
> +					pr_err("Failed to encrypt SYNIC msg page: %d\n", ret);
> +					hv_cpu->synic_message_page = NULL;
> +				}
> +			}
> +
> +			if (hv_cpu->synic_event_page) {
> +				ret = set_memory_encrypted((unsigned long)
> +					hv_cpu->synic_event_page, 1);
> +				if (ret) {
> +					pr_err("Failed to encrypt SYNIC event page: %d\n", ret);
> +					hv_cpu->synic_event_page = NULL;
> +				}
> +			}
> +		}
> +
>  		free_page((unsigned long)hv_cpu->synic_event_page);
>  		free_page((unsigned long)hv_cpu->synic_message_page);
>  	}
> @@ -179,7 +236,8 @@ void hv_synic_enable_regs(unsigned int cpu)
>  		if (!hv_cpu->synic_message_page)
>  			pr_err("Fail to map synic message page.\n");
>  	} else {
> -		simp.base_simp_gpa = virt_to_phys(hv_cpu->synic_message_page)
> +		simp.base_simp_gpa =
> +			cc_mkdec(virt_to_phys(hv_cpu->synic_message_page))
>  			>> HV_HYP_PAGE_SHIFT;
>  	}
> 
> @@ -198,7 +256,8 @@ void hv_synic_enable_regs(unsigned int cpu)
>  		if (!hv_cpu->synic_event_page)
>  			pr_err("Fail to map synic event page.\n");
>  	} else {
> -		siefp.base_siefp_gpa = virt_to_phys(hv_cpu->synic_event_page)
> +		siefp.base_siefp_gpa =
> +			cc_mkdec(virt_to_phys(hv_cpu->synic_event_page))
>  			>> HV_HYP_PAGE_SHIFT;
>  	}
> 
> --
> 2.25.1

Commit message nit notwithstanding --

Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>