| Message ID | 20241005-arm64-gcs-v14-4-59060cd6092b@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | KVM: arm64: Provide guest support for GCS | expand |
On Sat, 05 Oct 2024 11:37:31 +0100, Mark Brown <broonie@kernel.org> wrote: > > As per DDI 0487 RWTXBY we need to manage PSTATE.EXLOCK when entering an > exception, when the exception is entered from a lower EL the bit is cleared > while if entering from the same EL it is set to GCSCR_ELx.EXLOCKEN. > Implement this behaviour in enter_exception64(). > > Signed-off-by: Mark Brown <broonie@kernel.org> > --- > arch/arm64/include/uapi/asm/ptrace.h | 2 ++ > arch/arm64/kvm/hyp/exception.c | 10 ++++++++++ > 2 files changed, 12 insertions(+) > > diff --git a/arch/arm64/include/uapi/asm/ptrace.h b/arch/arm64/include/uapi/asm/ptrace.h > index 0f39ba4f3efd4a8760f0fca0fbf1a2563b191c7d..9987957f4f7137bf107653b817885bb976853a83 100644 > --- a/arch/arm64/include/uapi/asm/ptrace.h > +++ b/arch/arm64/include/uapi/asm/ptrace.h > @@ -37,6 +37,7 @@ > #define PSR_MODE_EL3t 0x0000000c > #define PSR_MODE_EL3h 0x0000000d > #define PSR_MODE_MASK 0x0000000f > +#define PSR_EL_MASK 0x0000000c > > /* AArch32 CPSR bits */ > #define PSR_MODE32_BIT 0x00000010 > @@ -56,6 +57,7 @@ > #define PSR_C_BIT 0x20000000 > #define PSR_Z_BIT 0x40000000 > #define PSR_N_BIT 0x80000000 > +#define PSR_EXLOCK_BIT 0x400000000 > > #define PSR_BTYPE_SHIFT 10 > > diff --git a/arch/arm64/kvm/hyp/exception.c b/arch/arm64/kvm/hyp/exception.c > index 424a5107cddb5e1cdd75ef3581adef03aaadabb7..0d41b9b75cf83250b2c0d20cd82c153869efb0e4 100644 > --- a/arch/arm64/kvm/hyp/exception.c > +++ b/arch/arm64/kvm/hyp/exception.c > @@ -160,6 +160,16 @@ static void enter_exception64(struct kvm_vcpu *vcpu, unsigned long target_mode, > // PSTATE.BTYPE is set to zero upon any exception to AArch64 > // See ARM DDI 0487E.a, pages D1-2293 to D1-2294. > > + // PSTATE.EXLOCK is set to 0 upon any exception to a higher > + // EL, or to GCSCR_ELx.EXLOCKEN for an exception to the same > + // exception level. See ARM DDI 0487 RWTXBY, D.1.3.2 in K.a. > + if (kvm_has_gcs(vcpu->kvm) && > + (target_mode & PSR_EL_MASK) == (mode & PSR_EL_MASK)) { > + u64 gcscr = __vcpu_read_sys_reg(vcpu, GCSCR_EL1); No, please. This only works by luck when a guest has AArch32 EL0, and creates more havoc on a NV guest. In general, this PSR_EL_MASK creates more problem than anything else, and doesn't fit the rest of the code. So this needs to: - explicitly only apply to exceptions from AArch64 - handle exception from EL2, since this helper already deals with that The latter point of course means introducing GCSCR_EL2 (and everything that depends on it, such as the trap handling). M.
On Sat, Oct 05, 2024 at 01:36:09PM +0100, Marc Zyngier wrote: > Mark Brown <broonie@kernel.org> wrote: > > + // PSTATE.EXLOCK is set to 0 upon any exception to a higher > > + // EL, or to GCSCR_ELx.EXLOCKEN for an exception to the same > > + // exception level. See ARM DDI 0487 RWTXBY, D.1.3.2 in K.a. > > + if (kvm_has_gcs(vcpu->kvm) && > > + (target_mode & PSR_EL_MASK) == (mode & PSR_EL_MASK)) { > > + u64 gcscr = __vcpu_read_sys_reg(vcpu, GCSCR_EL1); > No, please. This only works by luck when a guest has AArch32 EL0, and > creates more havoc on a NV guest. In general, this PSR_EL_MASK creates > more problem than anything else, and doesn't fit the rest of the code. You say luck, I say careful architecture definition but sure. > So this needs to: > - explicitly only apply to exceptions from AArch64 > - handle exception from EL2, since this helper already deals with that > The latter point of course means introducing GCSCR_EL2 (and everything > that depends on it, such as the trap handling). For clarity, which trap handling specifically?
On Sat, 05 Oct 2024 15:14:21 +0100, Mark Brown <broonie@kernel.org> wrote: > > On Sat, Oct 05, 2024 at 01:36:09PM +0100, Marc Zyngier wrote: > > Mark Brown <broonie@kernel.org> wrote: > > > > + // PSTATE.EXLOCK is set to 0 upon any exception to a higher > > > + // EL, or to GCSCR_ELx.EXLOCKEN for an exception to the same > > > + // exception level. See ARM DDI 0487 RWTXBY, D.1.3.2 in K.a. > > > + if (kvm_has_gcs(vcpu->kvm) && > > > + (target_mode & PSR_EL_MASK) == (mode & PSR_EL_MASK)) { > > > + u64 gcscr = __vcpu_read_sys_reg(vcpu, GCSCR_EL1); > > > No, please. This only works by luck when a guest has AArch32 EL0, and > > creates more havoc on a NV guest. In general, this PSR_EL_MASK creates > > more problem than anything else, and doesn't fit the rest of the code. > > You say luck, I say careful architecture definition but sure. I wasn't talking about the architecture, but sure. > > > So this needs to: > > - explicitly only apply to exceptions from AArch64 > > - handle exception from EL2, since this helper already deals with that > > > The latter point of course means introducing GCSCR_EL2 (and everything > > that depends on it, such as the trap handling). > > For clarity, which trap handling specifically? All the traps described in the GCSCR_EL2 documentation -- I see two control bits described in K.a, all of which needs to be propagated and their effects handled. Similarly, GCSPR_EL2 needs to be defined. M.
diff --git a/arch/arm64/include/uapi/asm/ptrace.h b/arch/arm64/include/uapi/asm/ptrace.h index 0f39ba4f3efd4a8760f0fca0fbf1a2563b191c7d..9987957f4f7137bf107653b817885bb976853a83 100644 --- a/arch/arm64/include/uapi/asm/ptrace.h +++ b/arch/arm64/include/uapi/asm/ptrace.h @@ -37,6 +37,7 @@ #define PSR_MODE_EL3t 0x0000000c #define PSR_MODE_EL3h 0x0000000d #define PSR_MODE_MASK 0x0000000f +#define PSR_EL_MASK 0x0000000c /* AArch32 CPSR bits */ #define PSR_MODE32_BIT 0x00000010 @@ -56,6 +57,7 @@ #define PSR_C_BIT 0x20000000 #define PSR_Z_BIT 0x40000000 #define PSR_N_BIT 0x80000000 +#define PSR_EXLOCK_BIT 0x400000000 #define PSR_BTYPE_SHIFT 10 diff --git a/arch/arm64/kvm/hyp/exception.c b/arch/arm64/kvm/hyp/exception.c index 424a5107cddb5e1cdd75ef3581adef03aaadabb7..0d41b9b75cf83250b2c0d20cd82c153869efb0e4 100644 --- a/arch/arm64/kvm/hyp/exception.c +++ b/arch/arm64/kvm/hyp/exception.c @@ -160,6 +160,16 @@ static void enter_exception64(struct kvm_vcpu *vcpu, unsigned long target_mode, // PSTATE.BTYPE is set to zero upon any exception to AArch64 // See ARM DDI 0487E.a, pages D1-2293 to D1-2294. + // PSTATE.EXLOCK is set to 0 upon any exception to a higher + // EL, or to GCSCR_ELx.EXLOCKEN for an exception to the same + // exception level. See ARM DDI 0487 RWTXBY, D.1.3.2 in K.a. + if (kvm_has_gcs(vcpu->kvm) && + (target_mode & PSR_EL_MASK) == (mode & PSR_EL_MASK)) { + u64 gcscr = __vcpu_read_sys_reg(vcpu, GCSCR_EL1); + if (gcscr & GCSCR_ELx_EXLOCKEN) + new |= PSR_EXLOCK_BIT; + } + new |= PSR_D_BIT; new |= PSR_A_BIT; new |= PSR_I_BIT;
As per DDI 0487 RWTXBY we need to manage PSTATE.EXLOCK when entering an exception, when the exception is entered from a lower EL the bit is cleared while if entering from the same EL it is set to GCSCR_ELx.EXLOCKEN. Implement this behaviour in enter_exception64(). Signed-off-by: Mark Brown <broonie@kernel.org> --- arch/arm64/include/uapi/asm/ptrace.h | 2 ++ arch/arm64/kvm/hyp/exception.c | 10 ++++++++++ 2 files changed, 12 insertions(+)