On Thu, 22 Feb 2024 13:11:59 +0000, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: > > On 2/22/24 12:40, Stephen Rothwell wrote: > >> This fails because https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git/commit/?id=fdd867fe9b32 > >> added new fields to that register (ID_AA64DFR1_EL1) > >> > >> and commit b80b701d5a6 ("KVM: arm64: Snapshot all non-zero RES0/RES1 sysreg fields for later checking") > >> took a snapshot of the fields, so the RES0 (reserved 0) bits don't match anymore. > >> > >> Not sure how to resolve it in the git branches though. > > > > Thanks. I will apply this patch to the merge of the kvm-arm tree from > > tomorrow (and at the end of today's tree). > > Marc, Oliver, can you get a topic branch from Catalin and friends for > this sysreg patch, and apply the fixup directly to the kvm-arm branch > in the merge commit? > > Not _necessary_, as I can always ask Linus to do the fixup, but > generally he prefers to have this sorted out by the maintainers if it > is detected by linux-next. I think that's not the correct thing to do at this time. I should have timed the introduction of these checks a bit later, after the merge window. But more to the point, the proposed patch is also not the best thing to merge, because it hides that there is a discrepancy between what the architecture describes, and what KVM knows. I really want to know about it, or it will be yet another bug that we wont detect easily. Specially for ID_AA64DFR*_EL1 which are a bloody mine-field. So I'd rather we make the check optional, and we'll play catch up for a bit longer. Something like the patch below. Oliver, do you mind queuing this ASAP (also pushed out to my dev branch)? Thanks, M. >From 85d861a6ca055c7681c826c580e7c90d74c26ac5 Mon Sep 17 00:00:00 2001 From: Marc Zyngier <maz@xxxxxxxxxx> Date: Thu, 22 Feb 2024 14:12:09 +0000 Subject: [PATCH] KVM: arm64: Make build-time check of RES0/RES1 bits optional In order to ease the transition towards a state of absolute paranoia where all RES0/RES1 bits gets checked against what KVM know of them, make the checks optional and garded by a config symbol (CONFIG_KVM_ARM64_RES_BITS_PARANOIA) default to n. Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx> --- arch/arm64/kvm/Kconfig | 11 +++++++++++ arch/arm64/kvm/check-res-bits.h | 4 ++++ 2 files changed, 15 insertions(+) diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig index 5c2a672c06a8..fa9389270cfe 100644 --- a/arch/arm64/kvm/Kconfig +++ b/arch/arm64/kvm/Kconfig @@ -67,4 +67,15 @@ config PROTECTED_NVHE_STACKTRACE If unsure, or not using protected nVHE (pKVM), say N. +config KVM_ARM64_RES_BITS_PARANOIA + bool "Build-time check of RES0/RES1 bits" + depends on KVM + default n + help + Say Y here to validate that KVM's knowledge of most system + registers' RES0/RES1 bits matches when the rest of the kernel + defines. Expect the build to fail badly if you enable this. + + Just say N. + endif # VIRTUALIZATION diff --git a/arch/arm64/kvm/check-res-bits.h b/arch/arm64/kvm/check-res-bits.h index 967b5d171d53..2d98e60efc3c 100644 --- a/arch/arm64/kvm/check-res-bits.h +++ b/arch/arm64/kvm/check-res-bits.h @@ -21,6 +21,8 @@ */ static inline void check_res_bits(void) { +#ifdef CONFIG_KVM_ARM64_RES_BITS_PARANOIA + BUILD_BUG_ON(OSDTRRX_EL1_RES0 != (GENMASK_ULL(63, 32))); BUILD_BUG_ON(MDCCINT_EL1_RES0 != (GENMASK_ULL(63, 31) | GENMASK_ULL(28, 0))); BUILD_BUG_ON(MDSCR_EL1_RES0 != (GENMASK_ULL(63, 36) | GENMASK_ULL(28, 28) | GENMASK_ULL(25, 24) | GENMASK_ULL(20, 20) | GENMASK_ULL(18, 16) | GENMASK_ULL(11, 7) | GENMASK_ULL(5, 1))); @@ -118,4 +120,6 @@ static inline void check_res_bits(void) BUILD_BUG_ON(TRBMAR_EL1_RES0 != (GENMASK_ULL(63, 12))); BUILD_BUG_ON(TRBTRG_EL1_RES0 != (GENMASK_ULL(63, 32))); BUILD_BUG_ON(TRBIDR_EL1_RES0 != (GENMASK_ULL(63, 12) | GENMASK_ULL(7, 6))); + +#endif } -- 2.39.2 -- Without deviation from the norm, progress is not possible.
