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s390/kvm: convert to regular kernel fpu user

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KVM modifies the kernel fpu's regs pointer to its own area to implement its
custom version of preemtible kernel fpu context. With general support for
preemptible kernel fpu context there is no need for the extra complexity in
KVM code anymore.

Therefore convert KVM to a regular kernel fpu user. In particular this
means that all TIF_FPU checks can be removed, since the fpu register
context will never be changed by other kernel fpu users, and also the fpu
register context will be restored if a thread is preempted.

Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
This commit is contained in:
Heiko Carstens 2024-02-03 11:45:13 +01:00
parent 4eed43de9b
commit ed3a0a011a
5 changed files with 22 additions and 26 deletions
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1
arch/s390/include/asm/kvm_host.h
View file

@ -743,7 +743,6 @@ struct kvm_vcpu_arch {
struct kvm_s390_sie_block *vsie_block;
unsigned int host_acrs[NUM_ACRS];
struct gs_cb *host_gscb;
struct fpu host_fpregs;
struct kvm_s390_local_interrupt local_int;
struct hrtimer ckc_timer;
struct kvm_s390_pgm_info pgm;

2
arch/s390/kernel/entry.S
View file

@ -220,8 +220,6 @@ SYM_FUNC_START(__sie64a)
oi __SIE_PROG0C+3(%r14),1 # we are going into SIE now
tm __SIE_PROG20+3(%r14),3 # last exit...
jnz .Lsie_skip
TSTMSK __SF_SIE_FLAGS(%r15),_TIF_FPU
jo .Lsie_skip # exit if fp/vx regs changed
lg %r14,__SF_SIE_CONTROL_PHYS(%r15) # get sie block phys addr
BPEXIT __SF_SIE_FLAGS(%r15),_TIF_ISOLATE_BP_GUEST
.Lsie_entry:

8
arch/s390/kvm/interrupt.c
View file

@ -584,7 +584,11 @@ static int __write_machine_check(struct kvm_vcpu *vcpu,
mci.val = mchk->mcic;
/* take care of lazy register loading */
save_user_fpu_regs();
fpu_stfpc(&vcpu->run->s.regs.fpc);
if (cpu_has_vx())
save_vx_regs((__vector128 *)&vcpu->run->s.regs.vrs);
else
save_fp_regs((freg_t *)&vcpu->run->s.regs.fprs);
save_access_regs(vcpu->run->s.regs.acrs);
if (MACHINE_HAS_GS && vcpu->arch.gs_enabled)
save_gs_cb(current->thread.gs_cb);
@ -648,7 +652,7 @@ static int __write_machine_check(struct kvm_vcpu *vcpu,
}
rc |= write_guest_lc(vcpu, __LC_GPREGS_SAVE_AREA,
vcpu->run->s.regs.gprs, 128);
rc |= put_guest_lc(vcpu, current->thread.ufpu.fpc,
rc |= put_guest_lc(vcpu, vcpu->run->s.regs.fpc,
(u32 __user *) __LC_FP_CREG_SAVE_AREA);
rc |= put_guest_lc(vcpu, vcpu->arch.sie_block->todpr,
(u32 __user *) __LC_TOD_PROGREG_SAVE_AREA);

34
arch/s390/kvm/kvm-s390.c
View file

@ -4829,8 +4829,6 @@ static int __vcpu_run(struct kvm_vcpu *vcpu)
vcpu->run->s.regs.gprs,
sizeof(sie_page->pv_grregs));
}
if (test_thread_flag(TIF_FPU))
load_user_fpu_regs();
exit_reason = sie64a(vcpu->arch.sie_block,
vcpu->run->s.regs.gprs);
if (kvm_s390_pv_cpu_is_protected(vcpu)) {
@ -4951,16 +4949,11 @@ static void sync_regs(struct kvm_vcpu *vcpu)
}
save_access_regs(vcpu->arch.host_acrs);
restore_access_regs(vcpu->run->s.regs.acrs);
/* save host (userspace) fprs/vrs */
save_user_fpu_regs();
vcpu->arch.host_fpregs.fpc = current->thread.ufpu.fpc;
vcpu->arch.host_fpregs.regs = current->thread.ufpu.regs;
fpu_lfpc_safe(&vcpu->run->s.regs.fpc);
if (cpu_has_vx())
current->thread.ufpu.regs = vcpu->run->s.regs.vrs;
load_vx_regs((__vector128 *)&vcpu->run->s.regs.vrs);
else
current->thread.ufpu.regs = vcpu->run->s.regs.fprs;
current->thread.ufpu.fpc = vcpu->run->s.regs.fpc;
load_fp_regs((freg_t *)&vcpu->run->s.regs.fprs);
/* Sync fmt2 only data */
if (likely(!kvm_s390_pv_cpu_is_protected(vcpu))) {
sync_regs_fmt2(vcpu);
@ -5021,12 +5014,11 @@ static void store_regs(struct kvm_vcpu *vcpu)
kvm_run->s.regs.pfc = vcpu->arch.pfault_compare;
save_access_regs(vcpu->run->s.regs.acrs);
restore_access_regs(vcpu->arch.host_acrs);
/* Save guest register state */
save_user_fpu_regs();
vcpu->run->s.regs.fpc = current->thread.ufpu.fpc;
/* Restore will be done lazily at return */
current->thread.ufpu.fpc = vcpu->arch.host_fpregs.fpc;
current->thread.ufpu.regs = vcpu->arch.host_fpregs.regs;
fpu_stfpc(&vcpu->run->s.regs.fpc);
if (cpu_has_vx())
save_vx_regs((__vector128 *)&vcpu->run->s.regs.vrs);
else
save_fp_regs((freg_t *)&vcpu->run->s.regs.fprs);
if (likely(!kvm_s390_pv_cpu_is_protected(vcpu)))
store_regs_fmt2(vcpu);
}
@ -5034,6 +5026,7 @@ static void store_regs(struct kvm_vcpu *vcpu)
int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
{
struct kvm_run *kvm_run = vcpu->run;
DECLARE_KERNEL_FPU_ONSTACK(fpu);
int rc;
/*
@ -5075,6 +5068,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
goto out;
}
kernel_fpu_begin(&fpu, KERNEL_FPC | KERNEL_VXR);
sync_regs(vcpu);
enable_cpu_timer_accounting(vcpu);
@ -5098,6 +5092,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
disable_cpu_timer_accounting(vcpu);
store_regs(vcpu);
kernel_fpu_end(&fpu, KERNEL_FPC | KERNEL_VXR);
kvm_sigset_deactivate(vcpu);
@ -5172,8 +5167,11 @@ int kvm_s390_vcpu_store_status(struct kvm_vcpu *vcpu, unsigned long addr)
* switch in the run ioctl. Let's update our copies before we save
* it into the save area
*/
save_user_fpu_regs();
vcpu->run->s.regs.fpc = current->thread.ufpu.fpc;
fpu_stfpc(&vcpu->run->s.regs.fpc);
if (cpu_has_vx())
save_vx_regs((__vector128 *)&vcpu->run->s.regs.vrs);
else
save_fp_regs((freg_t *)&vcpu->run->s.regs.fprs);
save_access_regs(vcpu->run->s.regs.acrs);
return kvm_s390_store_status_unloaded(vcpu, addr);

3
arch/s390/kvm/vsie.c
View file

@ -18,7 +18,6 @@
#include <asm/sclp.h>
#include <asm/nmi.h>
#include <asm/dis.h>
#include <asm/fpu.h>
#include <asm/facility.h>
#include "kvm-s390.h"
#include "gaccess.h"
@ -1149,8 +1148,6 @@ static int do_vsie_run(struct kvm_vcpu *vcpu, struct vsie_page *vsie_page)
*/
vcpu->arch.sie_block->prog0c |= PROG_IN_SIE;
barrier();
if (test_thread_flag(TIF_FPU))
load_user_fpu_regs();
if (!kvm_s390_vcpu_sie_inhibited(vcpu))
rc = sie64a(scb_s, vcpu->run->s.regs.gprs);
barrier();