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Subject[PATCH 5.4 08/18] drm/i915/gvt: Set SNOOP for PAT3 on BXT/APL to workaround GPU BB hang
Date
From: Colin Xu <colin.xu@intel.com>

commit 8fe105679765700378eb328495fcfe1566cdbbd0 upstream

If guest fills non-priv bb on ApolloLake/Broxton as Mesa i965 does in:
717e7539124d (i965: Use a WC map and memcpy for the batch instead of pw-)
Due to the missing flush of bb filled by VM vCPU, host GPU hangs on
executing these MI_BATCH_BUFFER.

Temporarily workaround this by setting SNOOP bit for PAT3 used by PPGTT
PML4 PTE: PAT(0) PCD(1) PWT(1).

The performance is still expected to be low, will need further improvement.

Acked-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Colin Xu <colin.xu@intel.com>
Signed-off-by: Zhenyu Wang <zhenyuw@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20201012045231.226748-1-colin.xu@intel.com
(cherry picked from commit 8fe105679765700378eb328495fcfe1566cdbbd0)
Signed-off-by: Colin Xu <colin.xu@intel.com>
Cc: <stable@vger.kernel.org> # 5.4.y
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/gpu/drm/i915/gvt/handlers.c | 32 +++++++++++++++++++++++++++++++-
1 file changed, 31 insertions(+), 1 deletion(-)

--- a/drivers/gpu/drm/i915/gvt/handlers.c
+++ b/drivers/gpu/drm/i915/gvt/handlers.c
@@ -1632,6 +1632,34 @@ static int edp_psr_imr_iir_write(struct
return 0;
}

+/**
+ * FixMe:
+ * If guest fills non-priv batch buffer on ApolloLake/Broxton as Mesa i965 did:
+ * 717e7539124d (i965: Use a WC map and memcpy for the batch instead of pwrite.)
+ * Due to the missing flush of bb filled by VM vCPU, host GPU hangs on executing
+ * these MI_BATCH_BUFFER.
+ * Temporarily workaround this by setting SNOOP bit for PAT3 used by PPGTT
+ * PML4 PTE: PAT(0) PCD(1) PWT(1).
+ * The performance is still expected to be low, will need further improvement.
+ */
+static int bxt_ppat_low_write(struct intel_vgpu *vgpu, unsigned int offset,
+ void *p_data, unsigned int bytes)
+{
+ u64 pat =
+ GEN8_PPAT(0, CHV_PPAT_SNOOP) |
+ GEN8_PPAT(1, 0) |
+ GEN8_PPAT(2, 0) |
+ GEN8_PPAT(3, CHV_PPAT_SNOOP) |
+ GEN8_PPAT(4, CHV_PPAT_SNOOP) |
+ GEN8_PPAT(5, CHV_PPAT_SNOOP) |
+ GEN8_PPAT(6, CHV_PPAT_SNOOP) |
+ GEN8_PPAT(7, CHV_PPAT_SNOOP);
+
+ vgpu_vreg(vgpu, offset) = lower_32_bits(pat);
+
+ return 0;
+}
+
static int mmio_read_from_hw(struct intel_vgpu *vgpu,
unsigned int offset, void *p_data, unsigned int bytes)
{
@@ -2778,7 +2806,7 @@ static int init_broadwell_mmio_info(stru

MMIO_DH(GEN6_PCODE_MAILBOX, D_BDW_PLUS, NULL, mailbox_write);

- MMIO_D(GEN8_PRIVATE_PAT_LO, D_BDW_PLUS);
+ MMIO_D(GEN8_PRIVATE_PAT_LO, D_BDW_PLUS & ~D_BXT);
MMIO_D(GEN8_PRIVATE_PAT_HI, D_BDW_PLUS);

MMIO_D(GAMTARBMODE, D_BDW_PLUS);
@@ -3281,6 +3309,8 @@ static int init_bxt_mmio_info(struct int

MMIO_DFH(GEN9_CTX_PREEMPT_REG, D_BXT, F_CMD_ACCESS, NULL, NULL);

+ MMIO_DH(GEN8_PRIVATE_PAT_LO, D_BXT, NULL, bxt_ppat_low_write);
+
return 0;
}


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