| Message ID | 20180104184334.16571-18-marc.zyngier@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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@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. > + va_mask |= region; > } > > static u32 compute_instruction(int n, u32 rd, u32 rn) > -- > 2.14.2 > Otherwise looks good: Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
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@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) >> -- >> 2.14.2 >> > Otherwise looks good: > > Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org> > Thanks, M.
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; - /* - * 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; + /* 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; + va_mask |= region; } static u32 compute_instruction(int n, u32 rd, u32 rn)
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@arm.com> --- arch/arm64/kvm/va_layout.c | 17 ++++++----------- 1 file changed, 6 insertions(+), 11 deletions(-)