Since ARMv8.0 the upper 32 bits of ESR_ELx have been RES0, and recently some of the upper bits gained a meaning and can be non-zero. For example, when FEAT_LS64 is implemented, ESR_ELx[36:32] contain ISS2, which for an ST64BV or ST64BV0 can be non-zero. This can be seen in ARM DDI 0487G.b, page D13-3145, section D13.2.37.
Generally, we must not rely on RES0 bit remaining zero in future, and when extracting ESR_ELx.EC we must mask out all other bits.
All C code uses the ESR_ELx_EC() macro, which masks out the irrelevant bits, and therefore no alterations are required to C code to avoid consuming irrelevant bits.
In a couple of places the KVM assembly extracts ESR_ELx.EC using LSR on an X register, and so could in theory consume previously RES0 bits. In both cases this is for comparison with EC values ESR_ELx_EC_HVC32 and ESR_ELx_EC_HVC64, for which the upper bits of ESR_ELx must currently be zero, but this could change in future.
This patch adjusts the KVM vectors to use UBFX rather than LSR to extract ESR_ELx.EC, ensuring these are robust to future additions to ESR_ELx.
Cc: stable@vger.kernel.org Signed-off-by: Mark Rutland mark.rutland@arm.com Cc: Alexandru Elisei alexandru.elisei@arm.com Cc: Catalin Marinas catalin.marinas@arm.com Cc: James Morse james.morse@arm.com Cc: Marc Zyngier maz@kernel.org Cc: Suzuki K Poulose suzuki.poulose@arm.com Cc: Will Deacon will@kernel.org --- arch/arm64/include/asm/esr.h | 1 + arch/arm64/kvm/hyp/hyp-entry.S | 2 +- arch/arm64/kvm/hyp/nvhe/host.S | 2 +- 3 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/arch/arm64/include/asm/esr.h b/arch/arm64/include/asm/esr.h index a305ce256090..d52a0b269ee8 100644 --- a/arch/arm64/include/asm/esr.h +++ b/arch/arm64/include/asm/esr.h @@ -68,6 +68,7 @@ #define ESR_ELx_EC_MAX (0x3F)
#define ESR_ELx_EC_SHIFT (26) +#define ESR_ELx_EC_WIDTH (6) #define ESR_ELx_EC_MASK (UL(0x3F) << ESR_ELx_EC_SHIFT) #define ESR_ELx_EC(esr) (((esr) & ESR_ELx_EC_MASK) >> ESR_ELx_EC_SHIFT)
diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S index 9aa9b73475c9..b6b6801d96d5 100644 --- a/arch/arm64/kvm/hyp/hyp-entry.S +++ b/arch/arm64/kvm/hyp/hyp-entry.S @@ -44,7 +44,7 @@ el1_sync: // Guest trapped into EL2
mrs x0, esr_el2 - lsr x0, x0, #ESR_ELx_EC_SHIFT + ubfx x0, x0, #ESR_ELx_EC_SHIFT, #ESR_ELx_EC_WIDTH cmp x0, #ESR_ELx_EC_HVC64 ccmp x0, #ESR_ELx_EC_HVC32, #4, ne b.ne el1_trap diff --git a/arch/arm64/kvm/hyp/nvhe/host.S b/arch/arm64/kvm/hyp/nvhe/host.S index 4b652ffb591d..d310d2b2c8b4 100644 --- a/arch/arm64/kvm/hyp/nvhe/host.S +++ b/arch/arm64/kvm/hyp/nvhe/host.S @@ -115,7 +115,7 @@ SYM_FUNC_END(__hyp_do_panic) .L__vect_start@: stp x0, x1, [sp, #-16]! mrs x0, esr_el2 - lsr x0, x0, #ESR_ELx_EC_SHIFT + ubfx x0, x0, #ESR_ELx_EC_SHIFT, #ESR_ELx_EC_WIDTH cmp x0, #ESR_ELx_EC_HVC64 b.ne __host_exit