[PATCH v4 24/40] KVM: arm64: Rewrite system register accessors to read/write functions
Christoffer Dall
christoffer.dall at linaro.org
Thu Feb 22 01:22:37 PST 2018
On Wed, Feb 21, 2018 at 01:32:45PM +0000, Marc Zyngier wrote:
> On Thu, 15 Feb 2018 21:03:16 +0000,
> Christoffer Dall wrote:
> >
> > From: Christoffer Dall <cdall at cs.columbia.edu>
> >
> > Currently we access the system registers array via the vcpu_sys_reg()
> > macro. However, we are about to change the behavior to some times
> > modify the register file directly, so let's change this to two
> > primitives:
> >
> > * Accessor macros vcpu_write_sys_reg() and vcpu_read_sys_reg()
> > * Direct array access macro __vcpu_sys_reg()
> >
> > The first primitive should be used in places where the code needs to
> > access the currently loaded VCPU's state as observed by the guest. For
> > example, when trapping on cache related registers, a write to a system
> > register should go directly to the VCPU version of the register.
> >
> > The second primitive can be used in places where the VCPU is known to
> > never be running (for example userspace access) or for registers which
> > are never context switched (for example all the PMU system registers).
> >
> > This rewrites all users of vcpu_sys_regs to one of the two primitives
> > above.
> >
> > No functional change.
> >
> > Signed-off-by: Christoffer Dall <cdall at cs.columbia.edu>
> > ---
> >
> > Notes:
> > Changes since v2:
> > - New patch (deferred register handling has been reworked)
> >
> > arch/arm64/include/asm/kvm_emulate.h | 13 ++++---
> > arch/arm64/include/asm/kvm_host.h | 13 ++++++-
> > arch/arm64/include/asm/kvm_mmu.h | 2 +-
> > arch/arm64/kvm/debug.c | 27 +++++++++-----
> > arch/arm64/kvm/inject_fault.c | 8 ++--
> > arch/arm64/kvm/sys_regs.c | 71 ++++++++++++++++++------------------
> > arch/arm64/kvm/sys_regs.h | 4 +-
> > arch/arm64/kvm/sys_regs_generic_v8.c | 4 +-
> > virt/kvm/arm/pmu.c | 37 ++++++++++---------
> > 9 files changed, 102 insertions(+), 77 deletions(-)
> >
> > diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
> > index 3cc535591bdf..d313aaae5c38 100644
> > --- a/arch/arm64/include/asm/kvm_emulate.h
> > +++ b/arch/arm64/include/asm/kvm_emulate.h
> > @@ -290,15 +290,18 @@ static inline int kvm_vcpu_sys_get_rt(struct kvm_vcpu *vcpu)
> >
> > static inline unsigned long kvm_vcpu_get_mpidr_aff(struct kvm_vcpu *vcpu)
> > {
> > - return vcpu_sys_reg(vcpu, MPIDR_EL1) & MPIDR_HWID_BITMASK;
> > + return vcpu_read_sys_reg(vcpu, MPIDR_EL1) & MPIDR_HWID_BITMASK;
> > }
> >
> > static inline void kvm_vcpu_set_be(struct kvm_vcpu *vcpu)
> > {
> > - if (vcpu_mode_is_32bit(vcpu))
> > + if (vcpu_mode_is_32bit(vcpu)) {
> > *vcpu_cpsr(vcpu) |= COMPAT_PSR_E_BIT;
> > - else
> > - vcpu_sys_reg(vcpu, SCTLR_EL1) |= (1 << 25);
> > + } else {
> > + u64 sctlr = vcpu_read_sys_reg(vcpu, SCTLR_EL1);
> > + sctlr |= (1 << 25);
> > + vcpu_write_sys_reg(vcpu, SCTLR_EL1, sctlr);
>
> General comment: it is slightly annoying that vcpu_write_sys_reg takes
> its parameters in an order different from that of write_sysreg
> (register followed with value, instead of value followed with
> register). Not a deal breaker, but slightly confusing.
>
Ah, I didn't compare to write_sysreg, I was thinking that
vcpu_read_sys_reg(vcpu, SCTLR_EL1);
vcpu_write_sys_reg(vcpu, SCTLR_EL1, val);
looked more symmetrical because the write just takes an extra value, but
I can see your argument as well.
I don't mind changing it if it matters to you?
> > + }
> > }
> >
> > static inline bool kvm_vcpu_is_be(struct kvm_vcpu *vcpu)
> > @@ -306,7 +309,7 @@ static inline bool kvm_vcpu_is_be(struct kvm_vcpu *vcpu)
> > if (vcpu_mode_is_32bit(vcpu))
> > return !!(*vcpu_cpsr(vcpu) & COMPAT_PSR_E_BIT);
> >
> > - return !!(vcpu_sys_reg(vcpu, SCTLR_EL1) & (1 << 25));
> > + return !!(vcpu_read_sys_reg(vcpu, SCTLR_EL1) & (1 << 25));
> > }
> >
> > static inline unsigned long vcpu_data_guest_to_host(struct kvm_vcpu *vcpu,
> > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> > index f2a6f39aec87..68398bf7882f 100644
> > --- a/arch/arm64/include/asm/kvm_host.h
> > +++ b/arch/arm64/include/asm/kvm_host.h
> > @@ -287,7 +287,18 @@ struct kvm_vcpu_arch {
> > };
> >
> > #define vcpu_gp_regs(v) (&(v)->arch.ctxt.gp_regs)
> > -#define vcpu_sys_reg(v,r) ((v)->arch.ctxt.sys_regs[(r)])
> > +
> > +/*
> > + * Only use __vcpu_sys_reg if you know you want the memory backed version of a
> > + * register, and not the one most recently accessed by a runnning VCPU. For
> > + * example, for userpace access or for system registers that are never context
> > + * switched, but only emulated.
> > + */
> > +#define __vcpu_sys_reg(v,r) ((v)->arch.ctxt.sys_regs[(r)])
> > +
> > +#define vcpu_read_sys_reg(v,r) __vcpu_sys_reg(v,r)
> > +#define vcpu_write_sys_reg(v,r,n) do { __vcpu_sys_reg(v,r) = n; } while (0)
> > +
> > /*
> > * CP14 and CP15 live in the same array, as they are backed by the
> > * same system registers.
> > diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
> > index 9679067a1574..95f46e73c4dc 100644
> > --- a/arch/arm64/include/asm/kvm_mmu.h
> > +++ b/arch/arm64/include/asm/kvm_mmu.h
> > @@ -249,7 +249,7 @@ struct kvm;
> >
> > static inline bool vcpu_has_cache_enabled(struct kvm_vcpu *vcpu)
> > {
> > - return (vcpu_sys_reg(vcpu, SCTLR_EL1) & 0b101) == 0b101;
> > + return (vcpu_read_sys_reg(vcpu, SCTLR_EL1) & 0b101) == 0b101;
> > }
> >
> > static inline void __clean_dcache_guest_page(kvm_pfn_t pfn, unsigned long size)
> > diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c
> > index feedb877cff8..db32d10a56a1 100644
> > --- a/arch/arm64/kvm/debug.c
> > +++ b/arch/arm64/kvm/debug.c
> > @@ -46,7 +46,8 @@ static DEFINE_PER_CPU(u32, mdcr_el2);
> > */
> > static void save_guest_debug_regs(struct kvm_vcpu *vcpu)
> > {
> > - vcpu->arch.guest_debug_preserved.mdscr_el1 = vcpu_sys_reg(vcpu, MDSCR_EL1);
> > + vcpu->arch.guest_debug_preserved.mdscr_el1 =
> > + vcpu_read_sys_reg(vcpu, MDSCR_EL1);
> >
> > trace_kvm_arm_set_dreg32("Saved MDSCR_EL1",
> > vcpu->arch.guest_debug_preserved.mdscr_el1);
> > @@ -54,10 +55,11 @@ static void save_guest_debug_regs(struct kvm_vcpu *vcpu)
> >
> > static void restore_guest_debug_regs(struct kvm_vcpu *vcpu)
> > {
> > - vcpu_sys_reg(vcpu, MDSCR_EL1) = vcpu->arch.guest_debug_preserved.mdscr_el1;
> > + vcpu_write_sys_reg(vcpu, MDSCR_EL1,
> > + vcpu->arch.guest_debug_preserved.mdscr_el1);
> >
> > trace_kvm_arm_set_dreg32("Restored MDSCR_EL1",
> > - vcpu_sys_reg(vcpu, MDSCR_EL1));
> > + vcpu_read_sys_reg(vcpu, MDSCR_EL1));
> > }
> >
> > /**
> > @@ -108,6 +110,7 @@ void kvm_arm_reset_debug_ptr(struct kvm_vcpu *vcpu)
> > void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
> > {
> > bool trap_debug = !(vcpu->arch.debug_flags & KVM_ARM64_DEBUG_DIRTY);
> > + unsigned long mdscr;
> >
> > trace_kvm_arm_setup_debug(vcpu, vcpu->guest_debug);
> >
> > @@ -152,9 +155,13 @@ void kvm_arm_setup_debug(struct kvm_vcpu *vcpu)
> > */
> > if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP) {
> > *vcpu_cpsr(vcpu) |= DBG_SPSR_SS;
> > - vcpu_sys_reg(vcpu, MDSCR_EL1) |= DBG_MDSCR_SS;
> > + mdscr = vcpu_read_sys_reg(vcpu, MDSCR_EL1);
> > + mdscr |= DBG_MDSCR_SS;
> > + vcpu_write_sys_reg(vcpu, MDSCR_EL1, mdscr);
>
> I have the feeling that we're going to need some clearbits/setbits
> variants of vcpu_write_sysreg at some point.
>
I can introduce these now if you prefer?
> It otherwise looks correct to me.
>
> Acked-by: Marc Zyngier <marc.zyngier at arm.com>
>
Thanks,
-Christoffer
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