[Xen-devel] [PATCH 1/2] x86/mwait_idle: stop using driver_data for static flags

["Jan Beulich" <JBeulich@xxxxxxxx>]

The (Linux) commit 4202735e8ab6ecfb0381631a0d0b58fefe0bd4e2
(cpuidle: Split cpuidle_state structure and move per-cpu statistics fields)
observed that the MWAIT flags for Cn on every processor to date were the
same, and created get_driver_data() to supply them.

Unfortunately, that assumption is false, going forward.
So here we restore the MWAIT flags to the cpuidle_state table.
However, instead restoring the old "driver_data" field,
we put the flags into the existing "flags" field,
where they probalby should have lived all along.

This patch does not change any operation.

Signed-off-by: Len Brown <len.brown@xxxxxxxxx>
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

--- a/xen/arch/x86/cpu/mwait-idle.c
+++ b/xen/arch/x86/cpu/mwait-idle.c
@@ -108,6 +108,16 @@ static const struct cpuidle_state {
 #define CPUIDLE_FLAG_TLB_FLUSHED       0x10000
 
 /*
+ * MWAIT takes an 8-bit "hint" in EAX "suggesting"
+ * the C-state (top nibble) and sub-state (bottom nibble)
+ * 0x00 means "MWAIT(C1)", 0x10 means "MWAIT(C2)" etc.
+ *
+ * We store the hint at the top of our "flags" for each state.
+ */
+#define flg2MWAIT(flags) (((flags) >> 24) & 0xFF)
+#define MWAIT2flg(eax) ((eax & 0xFF) << 24)
+
+/*
  * States are indexed by the cstate number,
  * which is also the index into the MWAIT hint array.
  * Thus C0 is a dummy.
@@ -116,18 +126,19 @@ static const struct cpuidle_state nehale
        { /* MWAIT C0 */ },
        { /* MWAIT C1 */
                .name = "C1-NHM",
+               .flags = MWAIT2flg(0x00),
                .exit_latency = 3,
                .target_residency = 6,
        },
        { /* MWAIT C2 */
                .name = "C3-NHM",
-               .flags = CPUIDLE_FLAG_TLB_FLUSHED,
+               .flags = MWAIT2flg(0x10) | CPUIDLE_FLAG_TLB_FLUSHED,
                .exit_latency = 20,
                .target_residency = 80,
        },
        { /* MWAIT C3 */
                .name = "C6-NHM",
-               .flags = CPUIDLE_FLAG_TLB_FLUSHED,
+               .flags = MWAIT2flg(0x20) | CPUIDLE_FLAG_TLB_FLUSHED,
                .exit_latency = 200,
                .target_residency = 800,
        }
@@ -137,24 +148,25 @@ static const struct cpuidle_state snb_cs
        { /* MWAIT C0 */ },
        { /* MWAIT C1 */
                .name = "C1-SNB",
+               .flags = MWAIT2flg(0x00),
                .exit_latency = 1,
                .target_residency = 1,
        },
        { /* MWAIT C2 */
                .name = "C3-SNB",
-               .flags = CPUIDLE_FLAG_TLB_FLUSHED,
+               .flags = MWAIT2flg(0x10) | CPUIDLE_FLAG_TLB_FLUSHED,
                .exit_latency = 80,
                .target_residency = 211,
        },
        { /* MWAIT C3 */
                .name = "C6-SNB",
-               .flags = CPUIDLE_FLAG_TLB_FLUSHED,
+               .flags = MWAIT2flg(0x20) | CPUIDLE_FLAG_TLB_FLUSHED,
                .exit_latency = 104,
                .target_residency = 345,
        },
        { /* MWAIT C4 */
                .name = "C7-SNB",
-               .flags = CPUIDLE_FLAG_TLB_FLUSHED,
+               .flags = MWAIT2flg(0x30) | CPUIDLE_FLAG_TLB_FLUSHED,
                .exit_latency = 109,
                .target_residency = 345,
        }
@@ -164,24 +176,25 @@ static const struct cpuidle_state ivb_cs
        { /* MWAIT C0 */ },
        { /* MWAIT C1 */
                .name = "C1-IVB",
+               .flags = MWAIT2flg(0x00),
                .exit_latency = 1,
                .target_residency = 1,
        },
        { /* MWAIT C2 */
                .name = "C3-IVB",
-               .flags = CPUIDLE_FLAG_TLB_FLUSHED,
+               .flags = MWAIT2flg(0x10) | CPUIDLE_FLAG_TLB_FLUSHED,
                .exit_latency = 59,
                .target_residency = 156,
        },
        { /* MWAIT C3 */
                .name = "C6-IVB",
-               .flags = CPUIDLE_FLAG_TLB_FLUSHED,
+               .flags = MWAIT2flg(0x20) | CPUIDLE_FLAG_TLB_FLUSHED,
                .exit_latency = 80,
                .target_residency = 300,
        },
        { /* MWAIT C4 */
                .name = "C7-IVB",
-               .flags = CPUIDLE_FLAG_TLB_FLUSHED,
+               .flags = MWAIT2flg(0x30) | CPUIDLE_FLAG_TLB_FLUSHED,
                .exit_latency = 87,
                .target_residency = 300,
        }
@@ -191,44 +204,32 @@ static const struct cpuidle_state atom_c
        { /* MWAIT C0 */ },
        { /* MWAIT C1 */
                .name = "C1-ATM",
+               .flags = MWAIT2flg(0x00),
                .exit_latency = 1,
                .target_residency = 4,
        },
        { /* MWAIT C2 */
                .name = "C2-ATM",
+               .flags = MWAIT2flg(0x10),
                .exit_latency = 20,
                .target_residency = 80,
        },
        { /* MWAIT C3 */ },
        { /* MWAIT C4 */
                .name = "C4-ATM",
-               .flags = CPUIDLE_FLAG_TLB_FLUSHED,
+               .flags = MWAIT2flg(0x30) | CPUIDLE_FLAG_TLB_FLUSHED,
                .exit_latency = 100,
                .target_residency = 400,
        },
        { /* MWAIT C5 */ },
        { /* MWAIT C6 */
                .name = "C6-ATM",
-               .flags = CPUIDLE_FLAG_TLB_FLUSHED,
+               .flags = MWAIT2flg(0x52) | CPUIDLE_FLAG_TLB_FLUSHED,
                .exit_latency = 140,
                .target_residency = 560,
        }
 };
 
-static u32 get_driver_data(unsigned int cstate)
-{
-       static const u32 driver_data[] = {
-               [1] /* MWAIT C1 */ = 0x00,
-               [2] /* MWAIT C2 */ = 0x10,
-               [3] /* MWAIT C3 */ = 0x20,
-               [4] /* MWAIT C4 */ = 0x30,
-               [5] /* MWAIT C5 */ = 0x40,
-               [6] /* MWAIT C6 */ = 0x52,
-       };
-
-       return driver_data[cstate < ARRAY_SIZE(driver_data) ? cstate : 0];
-}
-
 static void mwait_idle(void)
 {
        unsigned int cpu = smp_processor_id();
@@ -477,7 +478,7 @@ static int mwait_idle_cpu_init(struct no
 
                cx = dev->states + dev->count;
                cx->type = cstate;
-               cx->address = get_driver_data(cstate);
+               cx->address = flg2MWAIT(cpuidle_state_table[cstate].flags);
                cx->entry_method = ACPI_CSTATE_EM_FFH;
                cx->latency = cpuidle_state_table[cstate].exit_latency;
                cx->target_residency =

Attachment: x86-mwait-idle-flags.patch
Description: Text document

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