[xen staging] x86/mwait-idle: make SPR C1 and C1E be independent

[patchbot@xxxxxxx]

commit 171d4d24f829075cac83b6fafe7a4ed7c93935a6
Author:     Artem Bityutskiy <artem.bityutskiy@xxxxxxxxxxxxxxx>
AuthorDate: Thu Oct 13 17:56:13 2022 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Oct 13 17:56:13 2022 +0200

    x86/mwait-idle: make SPR C1 and C1E be independent
    
    This patch partially reverts the changes made by the following commit:
    
    da0e58c038e6 intel_idle: add 'preferred_cstates' module argument
    
    As that commit describes, on early Sapphire Rapids Xeon platforms the C1 and
    C1E states were mutually exclusive, so that users could only have either C1 
and
    C6, or C1E and C6.
    
    However, Intel firmware engineers managed to remove this limitation and 
make C1
    and C1E to be completely independent, just like on previous Xeon platforms.
    
    Therefore, this patch:
     * Removes commentary describing the old, and now non-existing SPR C1E
       limitation.
     * Marks SPR C1E as available by default.
     * Removes the 'preferred_cstates' parameter handling for SPR. Both C1 and
       C1E will be available regardless of 'preferred_cstates' value.
    
    We expect that all SPR systems are shipping with new firmware, which 
includes
    the C1/C1E improvement.
    
    Signed-off-by: Artem Bityutskiy <artem.bityutskiy@xxxxxxxxxxxxxxx>
    Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
    Origin: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 
1548fac47a11
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
    Release-acked-by: Henry Wang <Henry.Wang@xxxxxxx>
---
 xen/arch/x86/cpu/mwait-idle.c | 23 +----------------------
 1 file changed, 1 insertion(+), 22 deletions(-)

diff --git a/xen/arch/x86/cpu/mwait-idle.c b/xen/arch/x86/cpu/mwait-idle.c
index f5c83121a8..ffdc6fb2fc 100644
--- a/xen/arch/x86/cpu/mwait-idle.c
+++ b/xen/arch/x86/cpu/mwait-idle.c
@@ -689,16 +689,6 @@ static struct cpuidle_state __read_mostly adl_l_cstates[] 
= {
        {}
 };
 
-/*
- * On Sapphire Rapids Xeon C1 has to be disabled if C1E is enabled, and vice
- * versa. On SPR C1E is enabled only if "C1E promotion" bit is set in
- * MSR_IA32_POWER_CTL. But in this case there effectively no C1, because C1
- * requests are promoted to C1E. If the "C1E promotion" bit is cleared, then
- * both C1 and C1E requests end up with C1, so there is effectively no C1E.
- *
- * By default we enable C1 and disable C1E by marking it with
- * 'CPUIDLE_FLAG_DISABLED'.
- */
 static struct cpuidle_state __read_mostly spr_cstates[] = {
        {
                .name = "C1",
@@ -708,7 +698,7 @@ static struct cpuidle_state __read_mostly spr_cstates[] = {
        },
        {
                .name = "C1E",
-               .flags = MWAIT2flg(0x01) | CPUIDLE_FLAG_DISABLED,
+               .flags = MWAIT2flg(0x01),
                .exit_latency = 2,
                .target_residency = 4,
        },
@@ -1401,17 +1391,6 @@ static void __init spr_idle_state_table_update(void)
 {
        uint64_t msr;
 
-       /* Check if user prefers C1E over C1. */
-       if ((preferred_states_mask & BIT(2, U)) &&
-           !(preferred_states_mask & BIT(1, U))) {
-               /* Disable C1 and enable C1E. */
-               spr_cstates[0].flags |= CPUIDLE_FLAG_DISABLED;
-               spr_cstates[1].flags &= ~CPUIDLE_FLAG_DISABLED;
-
-               /* Request enabling C1E using the "C1E promotion" bit. */
-               idle_cpu_spr.c1e_promotion = C1E_PROMOTION_ENABLE;
-       }
-
        /*
         * By default, the C6 state assumes the worst-case scenario of package
         * C6. However, if PC6 is disabled, we update the numbers to match
--
generated by git-patchbot for /home/xen/git/xen.git#staging