Re: [PATCH v5 12/18] kvm: arm64: Configure VTCR_EL2.SL0 per VM

[Suzuki K Poulose]

Hi Eric,

On 20/09/18 15:25, Auger Eric wrote:
> Hi Suzuki,
> On 9/17/18 12:41 PM, Suzuki K Poulose wrote:
> > VTCR_EL2 holds the following key stage2 translation table
> > parameters:
> >    SL0  - Entry level in the page table lookup.
> >    T0SZ - Denotes the size of the memory addressed by the table.
> >
> > We have been using fixed values for the SL0 depending on the
> > page size as we have a fixed IPA size. But since we are about
> > to make it dynamic, we need to calculate the SL0 at runtime
> > per VM. This patch adds a helper to compute the value of SL0
> > for a VM based on the IPA size.
> >
> > Cc: Marc Zyngier <marc.zyngier@xxxxxxx>
> > Cc: Christoffer Dall <cdall@xxxxxxxxxx>
> > Cc: Eric Auger <eric.auger@xxxxxxxxxx>
> > Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> > ---
> > Changes since v3:
> >   - Update reference to latest ARM ARM.
> >   - Update per-vm VTCR value of SL0.
> >   - Add helpers to decode levels from SL0.
> >   - Didn't pick up Reviewed-by tag from Eric, as there
> >     are some new changes in this version


(-)
> > diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
> > index 3fb1d440be6e..5c1487dc5dca 100644
> > --- a/arch/arm64/include/asm/kvm_arm.h
> > +++ b/arch/arm64/include/asm/kvm_arm.h
> > @@ -121,7 +121,6 @@
> >   #define VTCR_EL2_IRGN0_WBWA        TCR_IRGN0_WBWA
> >   #define VTCR_EL2_SL0_SHIFT 6
> >   #define VTCR_EL2_SL0_MASK  (3 << VTCR_EL2_SL0_SHIFT)
> > -#define VTCR_EL2_SL0_LVL1   (1 << VTCR_EL2_SL0_SHIFT)
> >   #define VTCR_EL2_T0SZ_MASK 0x3f
> >   #define VTCR_EL2_VS_SHIFT  19
> >   #define VTCR_EL2_VS_8BIT   (0 << VTCR_EL2_VS_SHIFT)
> > @@ -148,29 +147,59 @@
> >   /*
> >    * Stage2 translation configuration:
> >    * 64kB pages (TG0 = 1)
> > - * 2 level page tables (SL = 1)
> >    */
> > -#define VTCR_EL2_TGRAN_FLAGS                (VTCR_EL2_TG0_64K | VTCR_EL2_SL0_LVL1)
> > -#define VTTBR_X_TGRAN_MAGIC         38
> > +#define VTCR_EL2_TGRAN                      VTCR_EL2_TG0_64K
> > +#define VTCR_EL2_TGRAN_SL0_BASE             3UL
> the name if not obvious. I understand this is yet another magic number
> used in the formulae below:
> SL0(PAGE_SIZE, Entry_level) = SL0_BASE(PAGE_SIZE) - Entry_Level
> I first tried to map this onto some spec fields. May be worth a comment?

Sure, I will make that clear.


> Besides
> Reviewed-by: Eric Auger <eric.auger@xxxxxxxxxx>

Thanks
Suzuki
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