Re: [PATCH v4 1/6] KVM: arm64: Correctly treat writes to OSLSR_EL1 as undefined
From: Mark Rutland <mark.rutland@arm.com>
Date: 2021-12-15 11:41:26
Also in:
kvm, kvmarm
Hi Oliver, On Tue, Dec 14, 2021 at 05:28:07PM +0000, Oliver Upton wrote:
Any valid implementation of the architecture should generate an undefined exception for writes to a read-only register, such as OSLSR_EL1. Nonetheless, the KVM handler actually implements write-ignore behavior. Align the trap handler for OSLSR_EL1 with hardware behavior. If such a write ever traps to EL2, inject an undef into the guest and print a warning.
I think this can still be read amibguously, since we don't explicitly state that writes to OSLSR_EL1 should never trap (and the implications of being UNDEFINED are subtle). How about: | Writes to OSLSR_EL1 are UNDEFINED and should never trap from EL1 to EL2, but | the KVM trap handler for OSLSR_EL1 handlees writes via ignore_write(). This | is confusing to readers of the code, but shouldn't have any functional impact. | | For clarity, use write_to_read_only() rather than ignore_write(). If a trap | is unexpectedly taken to EL2 in violation of the architecture, this will | WARN_ONCE() and inject an undef into the guest. With that: Reviewed-by: Mark Rutland <mark.rutland@arm.com> Mark.
quoted hunk ↗ jump to hunk
Reviewed-by: Reiji Watanabe <redacted> Signed-off-by: Oliver Upton <redacted> --- arch/arm64/kvm/sys_regs.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index e3ec1a44f94d..11b4212c2036 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c@@ -292,7 +292,7 @@ static bool trap_oslsr_el1(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r) { if (p->is_write) { - return ignore_write(vcpu, p); + return write_to_read_only(vcpu, p, r); } else { p->regval = (1 << 3); return true;-- 2.34.1.173.g76aa8bc2d0-goog _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
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