Re: [PATCH 1/3] KVM: arm64: Stash OSLSR_EL1 in the cpu context

Marc Zyngier
2021-10-29T11:27:42Z

On Fri, 29 Oct 2021 01:32:00 +0100,
Oliver Upton <oupton@google.com> wrote:
>
> An upcoming change to KVM will context switch the OS Lock status between
> guest/host. Add OSLSR_EL1 to the cpu context and handle guest reads
> using the stored value.
>
> Signed-off-by: Oliver Upton <oupton@google.com>
> ---
> arch/arm64/include/asm/kvm_host.h | 1 +
> arch/arm64/kvm/sys_regs.c | 13 ++++++-------
> 2 files changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index f8be56d5342b..c98f65c4a1f7 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -172,6 +172,7 @@ enum vcpu_sysreg {
> MDSCR_EL1, /* Monitor Debug System Control Register */
> MDCCINT_EL1, /* Monitor Debug Comms Channel Interrupt Enable Reg */
> DISR_EL1, /* Deferred Interrupt Status Register */
> + OSLSR_EL1, /* OS Lock Status Register */

Please move it one line up, next to the rest of the debug stuff
(DISR_EL1 is RAS and not debug).

>
> /* Performance Monitors Registers */
> PMCR_EL0, /* Control Register */
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 1d46e185f31e..0eb03e7508fe 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -291,12 +291,11 @@ static bool trap_oslsr_el1(struct kvm_vcpu *vcpu,
> struct sys_reg_params *p,
> const struct sys_reg_desc *r)
> {
> - if (p->is_write) {
> + if (p->is_write)
> return ignore_write(vcpu, p);

This should be UNDEF (though the HW should catch that, really).

> - } else {
> - p->regval = (1 << 3);
> - return true;
> - }
> +
> + p->regval = vcpu_read_sys_reg(vcpu, r->reg);
> + return true;
> }
>
> static bool trap_dbgauthstatus_el1(struct kvm_vcpu *vcpu,
> @@ -1441,7 +1440,7 @@ static const struct sys_reg_desc sys_reg_descs[] = {
>
> { SYS_DESC(SYS_MDRAR_EL1), trap_raz_wi },
> { SYS_DESC(SYS_OSLAR_EL1), trap_raz_wi },
> - { SYS_DESC(SYS_OSLSR_EL1), trap_oslsr_el1 },
> + { SYS_DESC(SYS_OSLSR_EL1), trap_oslsr_el1, reset_val, OSLSR_EL1, 0x00000008 },
> { SYS_DESC(SYS_OSDLR_EL1), trap_raz_wi },
> { SYS_DESC(SYS_DBGPRCR_EL1), trap_raz_wi },
> { SYS_DESC(SYS_DBGCLAIMSET_EL1), trap_raz_wi },
> @@ -1916,7 +1915,7 @@ static const struct sys_reg_desc cp14_regs[] = {
> { Op1( 0), CRn( 1), CRm( 0), Op2( 4), trap_raz_wi },
> DBGBXVR(1),
> /* DBGOSLSR */
> - { Op1( 0), CRn( 1), CRm( 1), Op2( 4), trap_oslsr_el1 },
> + { Op1( 0), CRn( 1), CRm( 1), Op2( 4), trap_oslsr_el1, NULL, OSLSR_EL1 },
> DBGBXVR(2),
> DBGBXVR(3),
> /* DBGOSDLR */

Please update tools/testing/selftests/kvm/aarch64/get-reg-list.c
before Andrew catches you red-handed! :D

M.

--
Without deviation from the norm, progress is not possible.