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[v6,4/8] RISC-V: KVM: Disable all hpmcounter access for VS/VU mode

Message ID 20230207095529.1787260-5-atishp@rivosinc.com (mailing list archive)
State New, archived
Headers show
Series KVM perf support | expand

Commit Message

Atish Kumar Patra Feb. 7, 2023, 9:55 a.m. UTC 
Any guest must not get access to any hpmcounter including cycle/instret
without any checks. We achieve that by disabling all the bits except TM
bit in hcounteren.

However, instret and cycle access for guest user space can be enabled
upon explicit request (via ONE REG) or on first trap from VU mode
to maintain ABI requirement in the future. This patch doesn't support
that as ONE REG interface is not settled yet.

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Atish Patra <atishp@rivosinc.com>
---
 arch/riscv/kvm/main.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
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Patch

diff --git a/arch/riscv/kvm/main.c b/arch/riscv/kvm/main.c
index 58c5489..c5d400f 100644
--- a/arch/riscv/kvm/main.c
+++ b/arch/riscv/kvm/main.c
@@ -49,7 +49,8 @@  int kvm_arch_hardware_enable(void)
 	hideleg |= (1UL << IRQ_VS_EXT);
 	csr_write(CSR_HIDELEG, hideleg);
 
-	csr_write(CSR_HCOUNTEREN, -1UL);
+	/* VS should access only the time counter directly. Everything else should trap */
+	csr_write(CSR_HCOUNTEREN, 0x02);
 
 	csr_write(CSR_HVIP, 0);