Re: [PATCH] target/arm: allow DC CVA[D]P in user mode emulation

[Zhuojia Shen]

On 05/16/2023 01:08 PM -0700, Richard Henderson wrote:
> On 5/15/23 20:59, Zhuojia Shen wrote:
> > DC CVAP and DC CVADP instructions can be executed in EL0 on Linux,
> > either directly when SCTLR_EL1.UCI == 1 or emulated by the kernel (see
> > user_cache_maint_handler() in arch/arm64/kernel/traps.c).  The Arm ARM
> > documents the semantics of the two instructions that they behave as
> > DC CVAC if the address pointed to by their register operand is not
> > persistent memory.
> > 
> > This patch enables execution of the two instructions in user mode
> > emulation as NOP while preserving their original emulation in full
> > system virtualization.
> > 
> > Signed-off-by: Zhuojia Shen <chaosdefinition@hotmail.com>
> > ---
> >   target/arm/helper.c               | 26 +++++++++++++-----
> >   tests/tcg/aarch64/Makefile.target | 11 ++++++++
> >   tests/tcg/aarch64/dcpodp.c        | 45 +++++++++++++++++++++++++++++++
> >   tests/tcg/aarch64/dcpop.c         | 45 +++++++++++++++++++++++++++++++
> >   4 files changed, 120 insertions(+), 7 deletions(-)
> >   create mode 100644 tests/tcg/aarch64/dcpodp.c
> >   create mode 100644 tests/tcg/aarch64/dcpop.c
> > 
> > diff --git a/target/arm/helper.c b/target/arm/helper.c
> > index 0b7fd2e7e6..eeba5e7978 100644
> > --- a/target/arm/helper.c
> > +++ b/target/arm/helper.c
> > @@ -7432,23 +7432,37 @@ static void dccvap_writefn(CPUARMState *env, const 
> > ARMCPRegInfo *opaque,
> >           }
> >       }
> >   }
> > +#endif /*CONFIG_USER_ONLY*/
> >   static const ARMCPRegInfo dcpop_reg[] = {
> >       { .name = "DC_CVAP", .state = ARM_CP_STATE_AA64,
> >         .opc0 = 1, .opc1 = 3, .crn = 7, .crm = 12, .opc2 = 1,
> > -      .access = PL0_W, .type = ARM_CP_NO_RAW | ARM_CP_SUPPRESS_TB_END,
> > +      .access = PL0_W,
> >         .fgt = FGT_DCCVAP,
> > -      .accessfn = aa64_cacheop_poc_access, .writefn = dccvap_writefn },
> > +      .accessfn = aa64_cacheop_poc_access,
> > +#ifdef CONFIG_USER_ONLY
> > +      .type = ARM_CP_NOP,
> > +#else
> > +      .type = ARM_CP_NO_RAW | ARM_CP_SUPPRESS_TB_END,
> > +      .writefn = dccvap_writefn,
> > +#endif
> > +    },
> >   };
> 
> Not quite correct, as CVAP to an unmapped address should SIGSEGV.  That'll
> be done by the probe_read within dccvap_writefn.
> 
> Need to make dccvap_writefn always present, ifdef out only the
> memory_region_from_host + memory_region_writeback from there.  Need to set
> SCTLR_EL1.UCI in arm_cpu_reset_hold in the CONFIG_USER_ONLY block.

Thanks for the reviews; I'll update in v2.

> 
> 
> r~
> 
> >   static const ARMCPRegInfo dcpodp_reg[] = {
> >       { .name = "DC_CVADP", .state = ARM_CP_STATE_AA64,
> >         .opc0 = 1, .opc1 = 3, .crn = 7, .crm = 13, .opc2 = 1,
> > -      .access = PL0_W, .type = ARM_CP_NO_RAW | ARM_CP_SUPPRESS_TB_END,
> > +      .access = PL0_W,
> >         .fgt = FGT_DCCVADP,
> > -      .accessfn = aa64_cacheop_poc_access, .writefn = dccvap_writefn },
> > +      .accessfn = aa64_cacheop_poc_access,
> > +#ifdef CONFIG_USER_ONLY
> > +      .type = ARM_CP_NOP,
> > +#else
> > +      .type = ARM_CP_NO_RAW | ARM_CP_SUPPRESS_TB_END,
> > +      .writefn = dccvap_writefn,
> > +#endif
> > +    },
> >   };
> > -#endif /*CONFIG_USER_ONLY*/
> >   static CPAccessResult access_aa64_tid5(CPUARMState *env, const 
> > ARMCPRegInfo *ri,
> >                                          bool isread)
> > @@ -9092,7 +9106,6 @@ void register_cp_regs_for_features(ARMCPU *cpu)
> >       if (cpu_isar_feature(aa64_tlbios, cpu)) {
> >           define_arm_cp_regs(cpu, tlbios_reginfo);
> >       }
> > -#ifndef CONFIG_USER_ONLY
> >       /* Data Cache clean instructions up to PoP */
> >       if (cpu_isar_feature(aa64_dcpop, cpu)) {
> >           define_one_arm_cp_reg(cpu, dcpop_reg);
> > @@ -9101,7 +9114,6 @@ void register_cp_regs_for_features(ARMCPU *cpu)
> >               define_one_arm_cp_reg(cpu, dcpodp_reg);
> >           }
> >       }
> > -#endif /*CONFIG_USER_ONLY*/
> >       /*
> >        * If full MTE is enabled, add all of the system registers.
> > diff --git a/tests/tcg/aarch64/Makefile.target 
> > b/tests/tcg/aarch64/Makefile.target
> > index 0315795487..3430fd3cd8 100644
> > --- a/tests/tcg/aarch64/Makefile.target
> > +++ b/tests/tcg/aarch64/Makefile.target
> > @@ -21,12 +21,23 @@ config-cc.mak: Makefile
> >     $(quiet-@)( \
> >         $(call cc-option,-march=armv8.1-a+sve,          CROSS_CC_HAS_SVE); \
> >         $(call cc-option,-march=armv8.1-a+sve2,         CROSS_CC_HAS_SVE2); 
> > \
> > +       $(call cc-option,-march=armv8.2-a,              
> > CROSS_CC_HAS_ARMV8_2); \
> >         $(call cc-option,-march=armv8.3-a,              
> > CROSS_CC_HAS_ARMV8_3); \
> > +       $(call cc-option,-march=armv8.5-a,              
> > CROSS_CC_HAS_ARMV8_5); \
> >         $(call cc-option,-mbranch-protection=standard,  
> > CROSS_CC_HAS_ARMV8_BTI); \
> >         $(call cc-option,-march=armv8.5-a+memtag,       
> > CROSS_CC_HAS_ARMV8_MTE); \
> >         $(call cc-option,-march=armv9-a+sme,            
> > CROSS_CC_HAS_ARMV9_SME)) 3> config-cc.mak
> >   -include config-cc.mak
> > +ifneq ($(CROSS_CC_HAS_ARMV8_2),)
> > +AARCH64_TESTS += dcpop
> > +dcpop: CFLAGS += -march=armv8.2-a
> > +endif
> > +ifneq ($(CROSS_CC_HAS_ARMV8_5),)
> > +AARCH64_TESTS += dcpodp
> > +dcpodp: CFLAGS += -march=armv8.5-a
> > +endif
> > +
> >   # Pauth Tests
> >   ifneq ($(CROSS_CC_HAS_ARMV8_3),)
> >   AARCH64_TESTS += pauth-1 pauth-2 pauth-4 pauth-5
> > diff --git a/tests/tcg/aarch64/dcpodp.c b/tests/tcg/aarch64/dcpodp.c
> > new file mode 100644
> > index 0000000000..dad61ce78c
> > --- /dev/null
> > +++ b/tests/tcg/aarch64/dcpodp.c
> > @@ -0,0 +1,45 @@
> > +/* Test execution of DC CVADP instruction */
> > +
> > +#include <asm/hwcap.h>
> > +#include <sys/auxv.h>
> > +
> > +#include <signal.h>
> > +#include <stdio.h>
> > +#include <stdlib.h>
> > +
> > +#ifndef HWCAP2_DCPODP
> > +#define HWCAP2_DCPODP (1 << 0)
> > +#endif
> > +
> > +static void sigill_handler(int sig)
> > +{
> > +    exit(EXIT_FAILURE);
> > +}
> > +
> > +static int do_dc_cvadp(void)
> > +{
> > +    struct sigaction sa = {
> > +        .sa_handler = sigill_handler,
> > +    };
> > +
> > +    if (sigaction(SIGILL, &sa, NULL) < 0) {
> > +        perror("sigaction");
> > +        return EXIT_FAILURE;
> > +    }
> > +
> > +    asm volatile("dc cvadp, %0\n\t" :: "r"(&sa));
> > +
> > +    return 0;
> > +}
> > +
> > +int main(void)
> > +{
> > +    if (getauxval(AT_HWCAP) & HWCAP2_DCPODP) {
> > +        return do_dc_cvadp();
> > +    } else {
> > +        printf("SKIP: no HWCAP2_DCPODP on this system\n");
> > +        return 0;
> > +    }
> > +
> > +    return 0;
> > +}
> > diff --git a/tests/tcg/aarch64/dcpop.c b/tests/tcg/aarch64/dcpop.c
> > new file mode 100644
> > index 0000000000..8b4ea7c91c
> > --- /dev/null
> > +++ b/tests/tcg/aarch64/dcpop.c
> > @@ -0,0 +1,45 @@
> > +/* Test execution of DC CVAP instruction */
> > +
> > +#include <asm/hwcap.h>
> > +#include <sys/auxv.h>
> > +
> > +#include <signal.h>
> > +#include <stdio.h>
> > +#include <stdlib.h>
> > +
> > +#ifndef HWCAP_DCPOP
> > +#define HWCAP_DCPOP (1 << 16)
> > +#endif
> > +
> > +static void sigill_handler(int sig)
> > +{
> > +    exit(EXIT_FAILURE);
> > +}
> > +
> > +static int do_dc_cvap(void)
> > +{
> > +    struct sigaction sa = {
> > +        .sa_handler = sigill_handler,
> > +    };
> > +
> > +    if (sigaction(SIGILL, &sa, NULL) < 0) {
> > +        perror("sigaction");
> > +        return EXIT_FAILURE;
> > +    }
> > +
> > +    asm volatile("dc cvap, %0\n\t" :: "r"(&sa));
> > +
> > +    return 0;
> > +}
> > +
> > +int main(void)
> > +{
> > +    if (getauxval(AT_HWCAP) & HWCAP_DCPOP) {
> > +        return do_dc_cvap();
> > +    } else {
> > +        printf("SKIP: no HWCAP_DCPOP on this system\n");
> > +        return 0;
> > +    }
> > +
> > +    return 0;
> > +}
>