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arm64: KVM: Dynamically patch the kernel/hyp VA mask

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So far, we're using a complicated sequence of alternatives to
patch the kernel/hyp VA mask on non-VHE, and NOP out the
masking altogether when on VHE.

The newly introduced dynamic patching gives us the opportunity
to simplify that code by patching a single instruction with
the correct mask (instead of the mind bending cumulative masking
we have at the moment) or even a single NOP on VHE. This also
adds some initial code that will allow the patching callback
to switch to a more complex patching.

Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: James Morse <james.morse@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
This commit is contained in:
Marc Zyngier
2017-12-03 17:36:55 +00:00
parent ef3935eeeb
commit 2b4d1606aa
3 changed files with 105 additions and 34 deletions
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46
arch/arm64/include/asm/kvm_mmu.h
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@@ -69,9 +69,6 @@
* mappings, and none of this applies in that case.
*/
#define HYP_PAGE_OFFSET_HIGH_MASK ((UL(1) << VA_BITS) - 1)
#define HYP_PAGE_OFFSET_LOW_MASK ((UL(1) << (VA_BITS - 1)) - 1)
#ifdef __ASSEMBLY__
#include <asm/alternative.h>
@@ -81,28 +78,15 @@
* Convert a kernel VA into a HYP VA.
* reg: VA to be converted.
*
* This generates the following sequences:
* - High mask:
* and x0, x0, #HYP_PAGE_OFFSET_HIGH_MASK
* nop
* - Low mask:
* and x0, x0, #HYP_PAGE_OFFSET_HIGH_MASK
* and x0, x0, #HYP_PAGE_OFFSET_LOW_MASK
* - VHE:
* nop
* nop
*
* The "low mask" version works because the mask is a strict subset of
* the "high mask", hence performing the first mask for nothing.
* Should be completely invisible on any viable CPU.
* The actual code generation takes place in kvm_update_va_mask, and
* the instructions below are only there to reserve the space and
* perform the register allocation (kvm_update_va_mask uses the
* specific registers encoded in the instructions).
*/
.macro kern_hyp_va reg
alternative_if_not ARM64_HAS_VIRT_HOST_EXTN
and \reg, \reg, #HYP_PAGE_OFFSET_HIGH_MASK
alternative_else_nop_endif
alternative_if ARM64_HYP_OFFSET_LOW
and \reg, \reg, #HYP_PAGE_OFFSET_LOW_MASK
alternative_else_nop_endif
alternative_cb kvm_update_va_mask
and \reg, \reg, #1
alternative_cb_end
.endm
#else
@@ -113,18 +97,14 @@ alternative_else_nop_endif
#include <asm/mmu_context.h>
#include <asm/pgtable.h>
void kvm_update_va_mask(struct alt_instr *alt,
__le32 *origptr, __le32 *updptr, int nr_inst);
static inline unsigned long __kern_hyp_va(unsigned long v)
{
asm volatile(ALTERNATIVE("and %0, %0, %1",
"nop",
ARM64_HAS_VIRT_HOST_EXTN)
: "+r" (v)
: "i" (HYP_PAGE_OFFSET_HIGH_MASK));
asm volatile(ALTERNATIVE("nop",
"and %0, %0, %1",
ARM64_HYP_OFFSET_LOW)
: "+r" (v)
: "i" (HYP_PAGE_OFFSET_LOW_MASK));
asm volatile(ALTERNATIVE_CB("and %0, %0, #1\n",
kvm_update_va_mask)
: "+r" (v));
return v;
}