On Thu, Feb 16, 2017 at 10:41:20AM +0000, Andre Przywara wrote:
> The ITS spec says that ITS commands are only processed when the ITS
> is enabled (section 8.19.4, Enabled, bit[0]). Our emulation was not taking
> this into account.
> Fix this by checking the enabled state before handling CWRITER writes.
>
> On the other hand that means that CWRITER could advance while the ITS
> is disabled, and enabling it would need those commands to be processed.
> Fix this case as well by refactoring actual command processing and
> calling this from both the GITS_CWRITER and GITS_CTLR handlers.
>
> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxx>
> ---
> virt/kvm/arm/vgic/vgic-its.c | 109 ++++++++++++++++++++++++++-----------------
> 1 file changed, 65 insertions(+), 44 deletions(-)
>
> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
> index 8c2b3cd..ff86106 100644
> --- a/virt/kvm/arm/vgic/vgic-its.c
> +++ b/virt/kvm/arm/vgic/vgic-its.c
> @@ -360,29 +360,6 @@ static int its_sync_lpi_pending_table(struct kvm_vcpu *vcpu)
> return ret;
> }
>
> -static unsigned long vgic_mmio_read_its_ctlr(struct kvm *vcpu,
> - struct vgic_its *its,
> - gpa_t addr, unsigned int len)
> -{
> - u32 reg = 0;
> -
> - mutex_lock(&its->cmd_lock);
> - if (its->creadr == its->cwriter)
> - reg |= GITS_CTLR_QUIESCENT;
> - if (its->enabled)
> - reg |= GITS_CTLR_ENABLE;
> - mutex_unlock(&its->cmd_lock);
> -
> - return reg;
> -}
> -
> -static void vgic_mmio_write_its_ctlr(struct kvm *kvm, struct vgic_its *its,
> - gpa_t addr, unsigned int len,
> - unsigned long val)
> -{
> - its->enabled = !!(val & GITS_CTLR_ENABLE);
> -}
> -
> static unsigned long vgic_mmio_read_its_typer(struct kvm *kvm,
> struct vgic_its *its,
> gpa_t addr, unsigned int len)
> @@ -1161,33 +1138,16 @@ static void vgic_mmio_write_its_cbaser(struct kvm *kvm, struct vgic_its *its,
> #define ITS_CMD_SIZE 32
> #define ITS_CMD_OFFSET(reg) ((reg) & GENMASK(19, 5))
>
> -/*
> - * By writing to CWRITER the guest announces new commands to be processed.
> - * To avoid any races in the first place, we take the its_cmd lock, which
> - * protects our ring buffer variables, so that there is only one user
> - * per ITS handling commands at a given time.
> - */
> -static void vgic_mmio_write_its_cwriter(struct kvm *kvm, struct vgic_its *its,
> - gpa_t addr, unsigned int len,
> - unsigned long val)
> +/* Must be called with the cmd_lock held. */
> +static void vgic_its_process_commands(struct kvm *kvm, struct vgic_its *its)
> {
> gpa_t cbaser;
> u64 cmd_buf[4];
> - u32 reg;
>
> - if (!its)
> - return;
> -
> - mutex_lock(&its->cmd_lock);
> -
> - reg = update_64bit_reg(its->cwriter, addr & 7, len, val);
> - reg = ITS_CMD_OFFSET(reg);
> - if (reg >= ITS_CMD_BUFFER_SIZE(its->cbaser)) {
> - mutex_unlock(&its->cmd_lock);
> + /* Commands are only processed when the ITS is enabled. */
> + if (!its->enabled)
> return;
> - }
>
> - its->cwriter = reg;
> cbaser = CBASER_ADDRESS(its->cbaser);
>
> while (its->cwriter != its->creadr) {
> @@ -1207,6 +1167,34 @@ static void vgic_mmio_write_its_cwriter(struct kvm *kvm, struct vgic_its *its,
> if (its->creadr == ITS_CMD_BUFFER_SIZE(its->cbaser))
> its->creadr = 0;
> }
> +}
> +
> +/*
> + * By writing to CWRITER the guest announces new commands to be processed.
> + * To avoid any races in the first place, we take the its_cmd lock, which
> + * protects our ring buffer variables, so that there is only one user
> + * per ITS handling commands at a given time.
> + */
> +static void vgic_mmio_write_its_cwriter(struct kvm *kvm, struct vgic_its *its,
> + gpa_t addr, unsigned int len,
> + unsigned long val)
> +{
> + u64 reg;
> +
> + if (!its)
> + return;
> +
> + mutex_lock(&its->cmd_lock);
> +
> + reg = update_64bit_reg(its->cwriter, addr & 7, len, val);
> + reg = ITS_CMD_OFFSET(reg);
> + if (reg >= ITS_CMD_BUFFER_SIZE(its->cbaser)) {
> + mutex_unlock(&its->cmd_lock);
> + return;
> + }
> + its->cwriter = reg;
> +
> + vgic_its_process_commands(kvm, its);
>
> mutex_unlock(&its->cmd_lock);
> }
> @@ -1287,6 +1275,39 @@ static void vgic_mmio_write_its_baser(struct kvm *kvm,
> *regptr = reg;
> }
>
> +static unsigned long vgic_mmio_read_its_ctlr(struct kvm *vcpu,
> + struct vgic_its *its,
> + gpa_t addr, unsigned int len)
> +{
> + u32 reg = 0;
> +
> + mutex_lock(&its->cmd_lock);
> + if (its->creadr == its->cwriter)
> + reg |= GITS_CTLR_QUIESCENT;
> + if (its->enabled)
> + reg |= GITS_CTLR_ENABLE;
> + mutex_unlock(&its->cmd_lock);
> +
> + return reg;
> +}
> +
> +static void vgic_mmio_write_its_ctlr(struct kvm *kvm, struct vgic_its *its,
> + gpa_t addr, unsigned int len,
> + unsigned long val)
> +{
> + mutex_lock(&its->cmd_lock);
> +
> + its->enabled = !!(val & GITS_CTLR_ENABLE);
> +
> + /*
> + * Try to process any pending commands. This function bails out early
> + * if the ITS is disabled or no commands have been queued.
> + */
> + vgic_its_process_commands(kvm, its);
> +
> + mutex_unlock(&its->cmd_lock);
> +}
> +
> #define REGISTER_ITS_DESC(off, rd, wr, length, acc) \
> { \
> .reg_offset = off, \
> --
> 2.9.0
>
Reviewed-by: Christoffer Dall <cdall@xxxxxxxxxx>
