From: Fuad Tabba <fuad.tabba@linux.dev>
To: Marc Zyngier <maz@kernel.org>, Oliver Upton <oupton@kernel.org>
Cc: Joey Gouly <joey.gouly@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
Zenghui Yu <yuzenghui@huawei.com>,
Steffen Eiden <seiden@linux.ibm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Fuad Tabba <tabba@google.com>,
kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org
Subject: [PATCH] KVM: arm64: Set HCR_EL2.BSU to Inner Shareable for guests
Date: Fri, 16 Oct 2026 09:15:58 +0100 [thread overview]
Message-ID: <20261016081558.805411-1-fuad.tabba@linux.dev> (raw)
KVM sets HCR_EL2.BSU to Inner Shareable for guests, so that a guest's
barriers cover the TLB and I-cache invalidations that HCR_EL2.FB
broadcasts. However, since HCR_BSU_IS became an alias of the generated
HCR_EL2_BSU_IS, it is the unshifted field value 0b01, which sets bit
0 (VM, already set) and leaves BSU at 0b00. A guest's DSB NSH is then
not required to wait for a broadcast TLBI to complete on other CPUs.
Build the field with SYS_FIELD_PREP_ENUM().
Fixes: d0f39259eff4 ("arm64: sysreg: Add layout for HCR_EL2")
Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
---
Found while testing Marc's HCR cleanup [1]. Its patch 1 carries this
line over as HCR_EL2_BSU_IS, so on top of this fix that hunk would
keep SYS_FIELD_PREP_ENUM() instead. I can also rebase this on top of
the series if that's easier.
[1] https://lore.kernel.org/r/20261015173605.1072963-1-maz@kernel.org
arch/arm64/include/asm/kvm_arm.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
index 4bfbd827c5aa7..b3e9dd302730e 100644
--- a/arch/arm64/include/asm/kvm_arm.h
+++ b/arch/arm64/include/asm/kvm_arm.h
@@ -98,7 +98,7 @@
* TID1: Trap REVIDR_EL1, AIDR_EL1, and SMIDR_EL1
*/
#define HCR_GUEST_FLAGS (HCR_TSC | HCR_TSW | HCR_TWE | HCR_TWI | HCR_VM | \
- HCR_BSU_IS | HCR_FB | HCR_TACR | \
+ SYS_FIELD_PREP_ENUM(HCR_EL2, BSU, IS) | HCR_EL2_FB | HCR_EL2_TACR | \
HCR_AMO | HCR_SWIO | HCR_TIDCP | HCR_RW | HCR_TLOR | \
HCR_FMO | HCR_IMO | HCR_PTW | HCR_TID3 | HCR_TID1)
#define HCR_HOST_NVHE_FLAGS (HCR_RW | HCR_API | HCR_APK)
--
2.39.5
next reply other threads:[~2026-10-16 8:16 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-16 8:15 Fuad Tabba [this message]
2026-10-16 10:10 ` [PATCH] KVM: arm64: Set HCR_EL2.BSU to Inner Shareable for guests Marc Zyngier
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