[PATCH v2 3/3] arm64: kvm: add support for the extended 64bit ccsidr
Marc Zyngier
marc.zyngier at arm.com
Wed Feb 1 08:02:53 PST 2017
On 30/01/17 16:25, Sudeep Holla wrote:
> csselr and ccsidr are treated as 64-bit values already elsewhere in the
> kernel. It also aligns well with the architecture extensions that allow
> 64-bit format for ccsidr.
>
> This patch upgrades the existing accesses to csselr and ccsidr from
> 32-bit to 64-bit in preparation to add support to those extensions.
> It also add dedicated KVM_REG_ARM_DEMUX_ID_EXT_CCSIDR demux register
> to handle 64-bit ccsidr in KVM.
>
> Cc: Christoffer Dall <christoffer.dall at linaro.org>
> Cc: Marc Zyngier <marc.zyngier at arm.com>
> Signed-off-by: Sudeep Holla <sudeep.holla at arm.com>
> ---
> arch/arm64/include/uapi/asm/kvm.h | 1 +
> arch/arm64/kvm/sys_regs.c | 104 ++++++++++++++++++++++++++++----------
> 2 files changed, 77 insertions(+), 28 deletions(-)
>
> v1->v2:
> - Added dependency on cpu_supports_ccsidr_64b_format(PATCH 1/3)
> - Added a new KVM_REG_ARM_DEMUX_ID_EXT_CCSIDR demux register id
> to support new 64bit CCSIDR
>
> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
> index 3051f86a9b5f..8aa18e65e6a5 100644
> --- a/arch/arm64/include/uapi/asm/kvm.h
> +++ b/arch/arm64/include/uapi/asm/kvm.h
> @@ -161,6 +161,7 @@ struct kvm_arch_memory_slot {
> #define KVM_REG_ARM_DEMUX_ID_MASK 0x000000000000FF00
> #define KVM_REG_ARM_DEMUX_ID_SHIFT 8
> #define KVM_REG_ARM_DEMUX_ID_CCSIDR (0x00 << KVM_REG_ARM_DEMUX_ID_SHIFT)
> +#define KVM_REG_ARM_DEMUX_ID_EXT_CCSIDR (0x01 << KVM_REG_ARM_DEMUX_ID_SHIFT)
> #define KVM_REG_ARM_DEMUX_VAL_MASK 0x00000000000000FF
> #define KVM_REG_ARM_DEMUX_VAL_SHIFT 0
>
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 72656743b4cc..f9822ac6d9ab 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -58,15 +58,15 @@
> */
>
> /* 3 bits per cache level, as per CLIDR, but non-existent caches always 0 */
> -static u32 cache_levels;
> +static u64 cache_levels;
>
> -/* CSSELR values; used to index KVM_REG_ARM_DEMUX_ID_CCSIDR */
> +/* CSSELR values; used to index KVM_REG_ARM_DEMUX_ID_{EXT_,}CCSIDR */
> #define CSSELR_MAX ((MAX_CACHE_LEVEL - 1) << 1)
>
> /* Which cache CCSIDR represents depends on CSSELR value. */
> -static u32 get_ccsidr(u32 csselr)
> +static u64 get_ccsidr(u64 csselr)
> {
> - u32 ccsidr;
> + u64 ccsidr;
>
> /* Make sure noone else changes CSSELR during this! */
> local_irq_disable();
> @@ -1952,9 +1952,9 @@ static int set_invariant_sys_reg(u64 id, void __user *uaddr)
> return 0;
> }
>
> -static bool is_valid_cache(u32 val)
> +static bool is_valid_cache(u64 val)
> {
> - u32 level, ctype;
> + u64 level, ctype;
>
> if (val >= CSSELR_MAX)
> return false;
> @@ -1977,10 +1977,28 @@ static bool is_valid_cache(u32 val)
> }
> }
>
> +static int demux_ccsidr_validate_get(u64 id, int size, u64 *val)
> +{
> + u64 cidx;
> +
> + if (KVM_REG_SIZE(id) != size)
> + return -ENOENT;
> +
> + cidx = (id & KVM_REG_ARM_DEMUX_VAL_MASK)
> + >> KVM_REG_ARM_DEMUX_VAL_SHIFT;
> + if (!is_valid_cache(cidx))
> + return -ENOENT;
> +
> + *val = get_ccsidr(cidx);
> + return 0;
> +}
> +
> static int demux_c15_get(u64 id, void __user *uaddr)
> {
> - u32 val;
> - u32 __user *uval = uaddr;
> + int ret;
> + u64 val;
> + u32 __user *uval;
> + u64 __user *uval64;
>
> /* Fail if we have unknown bits set. */
> if (id & ~(KVM_REG_ARCH_MASK|KVM_REG_SIZE_MASK|KVM_REG_ARM_COPROC_MASK
> @@ -1989,14 +2007,17 @@ static int demux_c15_get(u64 id, void __user *uaddr)
>
> switch (id & KVM_REG_ARM_DEMUX_ID_MASK) {
> case KVM_REG_ARM_DEMUX_ID_CCSIDR:
> - if (KVM_REG_SIZE(id) != 4)
> - return -ENOENT;
> - val = (id & KVM_REG_ARM_DEMUX_VAL_MASK)
> - >> KVM_REG_ARM_DEMUX_VAL_SHIFT;
> - if (!is_valid_cache(val))
> - return -ENOENT;
> -
> - return put_user(get_ccsidr(val), uval);
> + ret = demux_ccsidr_validate_get(id, sizeof(*uval), &val);
> + if (ret)
> + return ret;
> + uval = uaddr;
> + return put_user(val, uval);
> + case KVM_REG_ARM_DEMUX_ID_EXT_CCSIDR:
> + ret = demux_ccsidr_validate_get(id, sizeof(*uval64), &val);
> + if (ret)
> + return ret;
> + uval64 = uaddr;
> + return put_user(val, uval64);
> default:
> return -ENOENT;
> }
> @@ -2004,8 +2025,10 @@ static int demux_c15_get(u64 id, void __user *uaddr)
>
> static int demux_c15_set(u64 id, void __user *uaddr)
> {
> - u32 val, newval;
> - u32 __user *uval = uaddr;
> + int ret;
> + u64 val, newval;
> + u32 __user *uval;
> + u64 __user *uval64;
>
> /* Fail if we have unknown bits set. */
> if (id & ~(KVM_REG_ARCH_MASK|KVM_REG_SIZE_MASK|KVM_REG_ARM_COPROC_MASK
> @@ -2014,18 +2037,29 @@ static int demux_c15_set(u64 id, void __user *uaddr)
>
> switch (id & KVM_REG_ARM_DEMUX_ID_MASK) {
> case KVM_REG_ARM_DEMUX_ID_CCSIDR:
> - if (KVM_REG_SIZE(id) != 4)
> - return -ENOENT;
> - val = (id & KVM_REG_ARM_DEMUX_VAL_MASK)
> - >> KVM_REG_ARM_DEMUX_VAL_SHIFT;
> - if (!is_valid_cache(val))
> - return -ENOENT;
> + ret = demux_ccsidr_validate_get(id, sizeof(*uval), &val);
> + if (ret)
> + return ret;
>
> + uval = uaddr;
> if (get_user(newval, uval))
> return -EFAULT;
>
> /* This is also invariant: you can't change it. */
> - if (newval != get_ccsidr(val))
> + if (newval != val)
> + return -EINVAL;
> + return 0;
> + case KVM_REG_ARM_DEMUX_ID_EXT_CCSIDR:
> + ret = demux_ccsidr_validate_get(id, sizeof(*uval), &val);
> + if (ret)
> + return ret;
> +
> + uval64 = uaddr;
> + if (get_user(newval, uval64))
> + return -EFAULT;
> +
> + /* This is also invariant: you can't change it. */
> + if (newval != val)
> return -EINVAL;
> return 0;
> default:
> @@ -2086,12 +2120,10 @@ static unsigned int num_demux_regs(void)
> return count;
> }
>
> -static int write_demux_regids(u64 __user *uindices)
> +static int write_demux_ccsidr(u64 val, u64 __user *uindices)
> {
> - u64 val = KVM_REG_ARM64 | KVM_REG_SIZE_U32 | KVM_REG_ARM_DEMUX;
> unsigned int i;
>
> - val |= KVM_REG_ARM_DEMUX_ID_CCSIDR;
> for (i = 0; i < CSSELR_MAX; i++) {
> if (!is_valid_cache(i))
> continue;
> @@ -2099,9 +2131,25 @@ static int write_demux_regids(u64 __user *uindices)
> return -EFAULT;
> uindices++;
> }
> +
> return 0;
> }
>
> +static int write_demux_regids(u64 __user *uindices)
> +{
> + int ret;
> + u64 val = KVM_REG_ARM64 | KVM_REG_ARM_DEMUX;
> +
> + if (cpu_supports_ccsidr_64b_format())
> + /* 64 bit extended CCSIDR */
> + ret = write_demux_ccsidr(val | KVM_REG_ARM_DEMUX_ID_EXT_CCSIDR |
> + KVM_REG_SIZE_U64, uindices);
> + else
> + ret = write_demux_ccsidr(val | KVM_REG_ARM_DEMUX_ID_CCSIDR |
> + KVM_REG_SIZE_U32, uindices);
> + return ret;
> +}
> +
> static u64 sys_reg_to_index(const struct sys_reg_desc *reg)
> {
> return (KVM_REG_ARM64 | KVM_REG_SIZE_U64 |
> --
> 2.7.4
>
I'm a bit worried about this patch. If we snapshot a VM on a 32bit
CCSIDR system, and restore it on a 64bit CSSIDR system (or the reverse),
what happens? My hunch is that we cannot restore the VM properly.
Now, I'm questioning the need for having those altogether, as we do a
lot of work to prevent the guest from actually using that geometry (and
on a big-little system, this hardly works).
Christoffer, what do you think?
Thanks,
M.
--
Jazz is not dead. It just smells funny...
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