[PATCH v4 17/19] arm64: KVM: Dynamically compute the HYP VA mask
marc.zyngier at arm.com
Thu Feb 15 05:58:11 PST 2018
On 18/01/18 20:28, Christoffer Dall wrote:
> On Thu, Jan 04, 2018 at 06:43:32PM +0000, Marc Zyngier wrote:
>> As we're moving towards a much more dynamic way to compute our
>> HYP VA, let's express the mask in a slightly different way.
>> Instead of comparing the idmap position to the "low" VA mask,
>> we directly compute the mask by taking into account the idmap's
>> (VA_BIT-1) bit.
>> No functionnal change.
>> Signed-off-by: Marc Zyngier <marc.zyngier at arm.com>
>> arch/arm64/kvm/va_layout.c | 17 ++++++-----------
>> 1 file changed, 6 insertions(+), 11 deletions(-)
>> diff --git a/arch/arm64/kvm/va_layout.c b/arch/arm64/kvm/va_layout.c
>> index aee758574e61..75bb1c6772b0 100644
>> --- a/arch/arm64/kvm/va_layout.c
>> +++ b/arch/arm64/kvm/va_layout.c
>> @@ -21,24 +21,19 @@
>> #include <asm/insn.h>
>> #include <asm/kvm_mmu.h>
>> -#define HYP_PAGE_OFFSET_HIGH_MASK ((UL(1) << VA_BITS) - 1)
>> -#define HYP_PAGE_OFFSET_LOW_MASK ((UL(1) << (VA_BITS - 1)) - 1)
>> static u64 va_mask;
>> static void compute_layout(void)
>> phys_addr_t idmap_addr = __pa_symbol(__hyp_idmap_text_start);
>> - unsigned long mask = HYP_PAGE_OFFSET_HIGH_MASK;
>> + u64 region;
> the naming here really confused me. Would it make sense to call this
> 'hyp_va_msb' or something like that instead?
>> - /*
>> - * Activate the lower HYP offset only if the idmap doesn't
>> - * clash with it,
>> - */
>> - if (idmap_addr > HYP_PAGE_OFFSET_LOW_MASK)
>> - mask = HYP_PAGE_OFFSET_HIGH_MASK;
> Ah, the series was tested, it was just that this code only existed for a
> short while. Amusingly, I think this ephemeral bug goes against the "No
> function change" statement in the commit message.
>> + /* Where is my RAM region? */
>> + region = idmap_addr & BIT(VA_BITS - 1);
>> + region ^= BIT(VA_BITS - 1);
>> - va_mask = mask;
>> + va_mask = BIT(VA_BITS - 1) - 1;
> nit: This could also be written as GENMASK_ULL(VA_BITS - 2, 0) --- and
> now I'm not sure which one I prefer.
Good point. I think GENMASK makes it clearer what the intent is, and
assigning a mask to a mask has certain degree of consistency (/me fondly
remembers dimensional analysis...).
>> + va_mask |= region;
>> static u32 compute_instruction(int n, u32 rd, u32 rn)
> Otherwise looks good:
> Reviewed-by: Christoffer Dall <christoffer.dall at linaro.org>
Jazz is not dead. It just smells funny...
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