qemu-devel.nongnu.org archive mirror
 help / color / mirror / Atom feed
From: "Cédric Le Goater" <clg@kaod.org>
To: qemu-ppc@nongnu.org
Cc: David Gibson <david@gibson.dropbear.id.au>,
	Alexander Graf <agraf@suse.de>,
	qemu-devel@nongnu.org,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Cedric Le Goater <clg@kaod.org>
Subject: [Qemu-devel] [PATCH v2 10/10] ppc: Add P7/P8 Power Management instructions
Date: Tue, 21 Jun 2016 23:48:55 +0200	[thread overview]
Message-ID: <1466545735-2555-11-git-send-email-clg@kaod.org> (raw)
In-Reply-To: <1466545735-2555-1-git-send-email-clg@kaod.org>

From: Benjamin Herrenschmidt <benh@kernel.crashing.org>

This adds the ISA 2.06 and later power management instructions
(doze, nap, sleep and rvwinkle) and associated wakeup cause testing
in LPCR

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
[clg: fixed checkpatch.pl errors ]
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
---
 target-ppc/cpu-qom.h        |  9 +++++
 target-ppc/cpu.h            | 17 ++++++++-
 target-ppc/excp_helper.c    | 59 +++++++++++++++++++++++++++++
 target-ppc/helper.h         |  1 +
 target-ppc/translate.c      | 66 ++++++++++++++++++++++++++++++++
 target-ppc/translate_init.c | 92 ++++++++++++++++++++++++++++++++++++++++++++-
 6 files changed, 241 insertions(+), 3 deletions(-)

diff --git a/target-ppc/cpu-qom.h b/target-ppc/cpu-qom.h
index 969ecdfbd40a..0fad2def0a94 100644
--- a/target-ppc/cpu-qom.h
+++ b/target-ppc/cpu-qom.h
@@ -126,6 +126,15 @@ enum powerpc_excp_t {
 };
 
 /*****************************************************************************/
+/* PM instructions */
+typedef enum {
+    PPC_PM_DOZE,
+    PPC_PM_NAP,
+    PPC_PM_SLEEP,
+    PPC_PM_RVWINKLE,
+} powerpc_pm_insn_t;
+
+/*****************************************************************************/
 /* Input pins model                                                          */
 typedef enum powerpc_input_t powerpc_input_t;
 enum powerpc_input_t {
diff --git a/target-ppc/cpu.h b/target-ppc/cpu.h
index 61a24b19ffce..b1354a4791db 100644
--- a/target-ppc/cpu.h
+++ b/target-ppc/cpu.h
@@ -383,6 +383,14 @@ struct ppc_slb_t {
 #define LPCR_LPES1        (1ull << (63 - 61))
 #define LPCR_AIL_SHIFT    (63 - 40)      /* Alternate interrupt location */
 #define LPCR_AIL          (3ull << LPCR_AIL_SHIFT)
+#define LPCR_P7_PECE0     (1ull << (63 - 49))
+#define LPCR_P7_PECE1     (1ull << (63 - 50))
+#define LPCR_P7_PECE2     (1ull << (63 - 51))
+#define LPCR_P8_PECE0     (1ull << (63 - 47))
+#define LPCR_P8_PECE1     (1ull << (63 - 48))
+#define LPCR_P8_PECE2     (1ull << (63 - 49))
+#define LPCR_P8_PECE3     (1ull << (63 - 50))
+#define LPCR_P8_PECE4     (1ull << (63 - 51))
 
 #define msr_sf   ((env->msr >> MSR_SF)   & 1)
 #define msr_isf  ((env->msr >> MSR_ISF)  & 1)
@@ -1059,6 +1067,11 @@ struct CPUPPCState {
      * instructions and SPRs are diallowed if MSR:HV is 0
      */
     bool has_hv_mode;
+    /* On P7/P8, set when in PM state, we need to handle resume
+     * in a special way (such as routing some resume causes to
+     * 0x100), so flag this here.
+     */
+    bool in_pm_state;
 #endif
 
     /* Those resources are used only during code translation */
@@ -2068,6 +2081,8 @@ enum {
     PPC2_FP_CVT_S64    = 0x0000000000010000ULL,
     /* Transactional Memory (ISA 2.07, Book II)                              */
     PPC2_TM            = 0x0000000000020000ULL,
+    /* Server PM instructgions (ISA 2.06, Book III)                          */
+    PPC2_PM_ISA206     = 0x0000000000040000ULL,
 
 #define PPC_TCG_INSNS2 (PPC2_BOOKE206 | PPC2_VSX | PPC2_PRCNTL | PPC2_DBRX | \
                         PPC2_ISA205 | PPC2_VSX207 | PPC2_PERM_ISA206 | \
@@ -2075,7 +2090,7 @@ enum {
                         PPC2_FP_CVT_ISA206 | PPC2_FP_TST_ISA206 | \
                         PPC2_BCTAR_ISA207 | PPC2_LSQ_ISA207 | \
                         PPC2_ALTIVEC_207 | PPC2_ISA207S | PPC2_DFP | \
-                        PPC2_FP_CVT_S64 | PPC2_TM)
+                        PPC2_FP_CVT_S64 | PPC2_TM | PPC2_PM_ISA206)
 };
 
 /*****************************************************************************/
diff --git a/target-ppc/excp_helper.c b/target-ppc/excp_helper.c
index 054c12de3bff..533866b87b60 100644
--- a/target-ppc/excp_helper.c
+++ b/target-ppc/excp_helper.c
@@ -101,6 +101,44 @@ static inline void powerpc_excp(PowerPCCPU *cpu, int excp_model, int excp)
     asrr0 = -1;
     asrr1 = -1;
 
+    /* check for special resume at 0x100 from doze/nap/sleep/winkle on P7/P8 */
+    if (env->in_pm_state) {
+        env->in_pm_state = false;
+
+        /* Pretend to be returning from doze always as we don't lose state */
+        msr |= (0x1ull << (63 - 47));
+
+        /* Non-machine check are routed to 0x100 with a wakeup cause
+         * encoded in SRR1
+         */
+        if (excp != POWERPC_EXCP_MCHECK) {
+            switch (excp) {
+            case POWERPC_EXCP_RESET:
+                msr |= 0x4ull << (63 - 45);
+                break;
+            case POWERPC_EXCP_EXTERNAL:
+                msr |= 0x8ull << (63 - 45);
+                break;
+            case POWERPC_EXCP_DECR:
+                msr |= 0x6ull << (63 - 45);
+                break;
+            case POWERPC_EXCP_SDOOR:
+                msr |= 0x5ull << (63 - 45);
+                break;
+            case POWERPC_EXCP_SDOOR_HV:
+                msr |= 0x3ull << (63 - 45);
+                break;
+            case POWERPC_EXCP_HV_MAINT:
+                msr |= 0xaull << (63 - 45);
+                break;
+            default:
+                cpu_abort(cs, "Unsupported exception %d in Power Save mode\n",
+                          excp);
+            }
+            excp = POWERPC_EXCP_RESET;
+        }
+    }
+
     /* Exception targetting modifiers
      *
      * LPES0 is supported on POWER7/8
@@ -897,6 +935,27 @@ void helper_store_msr(CPUPPCState *env, target_ulong val)
     }
 }
 
+#if defined(TARGET_PPC64)
+void helper_pminsn(CPUPPCState *env, powerpc_pm_insn_t insn)
+{
+    CPUState *cs;
+
+    cs = CPU(ppc_env_get_cpu(env));
+    cs->halted = 1;
+    env->in_pm_state = true;
+
+    /* Technically, nap doesn't set EE, but if we don't set it
+     * then ppc_hw_interrupt() won't deliver. We could add some
+     * other tests there based on LPCR but it's simpler to just
+     * whack EE in. It will be cleared by the 0x100 at wakeup
+     * anyway. It will still be observable by the guest in SRR1
+     * but this doesn't seem to be a problem.
+     */
+    env->msr |= (1ull << MSR_EE);
+    helper_raise_exception(env, EXCP_HLT);
+}
+#endif /* defined(TARGET_PPC64) */
+
 static inline void do_rfi(CPUPPCState *env, target_ulong nip, target_ulong msr)
 {
     CPUState *cs = CPU(ppc_env_get_cpu(env));
diff --git a/target-ppc/helper.h b/target-ppc/helper.h
index f4410a836954..ab9592926f7b 100644
--- a/target-ppc/helper.h
+++ b/target-ppc/helper.h
@@ -13,6 +13,7 @@ DEF_HELPER_1(rfci, void, env)
 DEF_HELPER_1(rfdi, void, env)
 DEF_HELPER_1(rfmci, void, env)
 #if defined(TARGET_PPC64)
+DEF_HELPER_2(pminsn, void, env, i32)
 DEF_HELPER_1(rfid, void, env)
 DEF_HELPER_1(hrfid, void, env)
 #endif
diff --git a/target-ppc/translate.c b/target-ppc/translate.c
index 365fe3d34461..b94f0dff0307 100644
--- a/target-ppc/translate.c
+++ b/target-ppc/translate.c
@@ -3571,6 +3571,68 @@ static void gen_wait(DisasContext *ctx)
     gen_exception_err(ctx, EXCP_HLT, 1);
 }
 
+#if defined(TARGET_PPC64)
+static void gen_doze(DisasContext *ctx)
+{
+#if defined(CONFIG_USER_ONLY)
+    GEN_PRIV;
+#else
+    TCGv_i32 t;
+
+    CHK_HV;
+    t = tcg_const_i32(PPC_PM_DOZE);
+    gen_helper_pminsn(cpu_env, t);
+    tcg_temp_free_i32(t);
+    gen_stop_exception(ctx);
+#endif /* defined(CONFIG_USER_ONLY) */
+}
+
+static void gen_nap(DisasContext *ctx)
+{
+#if defined(CONFIG_USER_ONLY)
+    GEN_PRIV;
+#else
+    TCGv_i32 t;
+
+    CHK_HV;
+    t = tcg_const_i32(PPC_PM_NAP);
+    gen_helper_pminsn(cpu_env, t);
+    tcg_temp_free_i32(t);
+    gen_stop_exception(ctx);
+#endif /* defined(CONFIG_USER_ONLY) */
+}
+
+static void gen_sleep(DisasContext *ctx)
+{
+#if defined(CONFIG_USER_ONLY)
+    GEN_PRIV;
+#else
+    TCGv_i32 t;
+
+    CHK_HV;
+    t = tcg_const_i32(PPC_PM_SLEEP);
+    gen_helper_pminsn(cpu_env, t);
+    tcg_temp_free_i32(t);
+    gen_stop_exception(ctx);
+#endif /* defined(CONFIG_USER_ONLY) */
+}
+
+static void gen_rvwinkle(DisasContext *ctx)
+{
+#if defined(CONFIG_USER_ONLY)
+    GEN_PRIV;
+#else
+    TCGv_i32 t;
+
+    CHK_HV;
+    t = tcg_const_i32(PPC_PM_RVWINKLE);
+    gen_helper_pminsn(cpu_env, t);
+    tcg_temp_free_i32(t);
+    gen_stop_exception(ctx);
+#endif /* defined(CONFIG_USER_ONLY) */
+}
+#endif /* #if defined(TARGET_PPC64) */
+
 /***                         Floating-point load                           ***/
 #define GEN_LDF(name, ldop, opc, type)                                        \
 static void glue(gen_, name)(DisasContext *ctx)                                       \
@@ -9883,6 +9945,10 @@ GEN_HANDLER(mcrf, 0x13, 0x00, 0xFF, 0x00000001, PPC_INTEGER),
 GEN_HANDLER(rfi, 0x13, 0x12, 0x01, 0x03FF8001, PPC_FLOW),
 #if defined(TARGET_PPC64)
 GEN_HANDLER(rfid, 0x13, 0x12, 0x00, 0x03FF8001, PPC_64B),
+GEN_HANDLER_E(doze, 0x13, 0x12, 0x0c, 0x03FFF801, PPC_NONE, PPC2_PM_ISA206),
+GEN_HANDLER_E(nap, 0x13, 0x12, 0x0d, 0x03FFF801, PPC_NONE, PPC2_PM_ISA206),
+GEN_HANDLER_E(sleep, 0x13, 0x12, 0x0e, 0x03FFF801, PPC_NONE, PPC2_PM_ISA206),
+GEN_HANDLER_E(rvwinkle, 0x13, 0x12, 0x0f, 0x03FFF801, PPC_NONE, PPC2_PM_ISA206),
 GEN_HANDLER(hrfid, 0x13, 0x12, 0x08, 0x03FF8001, PPC_64H),
 #endif
 GEN_HANDLER(sc, 0x11, 0xFF, 0xFF, 0x03FFF01D, PPC_FLOW),
diff --git a/target-ppc/translate_init.c b/target-ppc/translate_init.c
index 6f2f760728bb..0b39a088458d 100644
--- a/target-ppc/translate_init.c
+++ b/target-ppc/translate_init.c
@@ -8371,10 +8371,45 @@ static bool ppc_pvr_match_power7(PowerPCCPUClass *pcc, uint32_t pvr)
     return false;
 }
 
+static bool cpu_has_work_POWER7(CPUState *cs)
+{
+    PowerPCCPU *cpu = POWERPC_CPU(cs);
+    CPUPPCState *env = &cpu->env;
+
+    if (cs->halted) {
+        if (!(cs->interrupt_request & CPU_INTERRUPT_HARD)) {
+            return false;
+        }
+        if ((env->pending_interrupts & (1u << PPC_INTERRUPT_EXT)) &&
+            (env->spr[SPR_LPCR] & LPCR_P7_PECE0)) {
+            return true;
+        }
+        if ((env->pending_interrupts & (1u << PPC_INTERRUPT_DECR)) &&
+            (env->spr[SPR_LPCR] & LPCR_P7_PECE1)) {
+            return true;
+        }
+        if ((env->pending_interrupts & (1u << PPC_INTERRUPT_MCK)) &&
+            (env->spr[SPR_LPCR] & LPCR_P7_PECE2)) {
+            return true;
+        }
+        if ((env->pending_interrupts & (1u << PPC_INTERRUPT_HMI)) &&
+            (env->spr[SPR_LPCR] & LPCR_P7_PECE2)) {
+            return true;
+        }
+        if (env->pending_interrupts & (1u << PPC_INTERRUPT_RESET)) {
+            return true;
+        }
+        return false;
+    } else {
+        return msr_ee && (cs->interrupt_request & CPU_INTERRUPT_HARD);
+    }
+}
+
 POWERPC_FAMILY(POWER7)(ObjectClass *oc, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(oc);
     PowerPCCPUClass *pcc = POWERPC_CPU_CLASS(oc);
+    CPUClass *cc = CPU_CLASS(oc);
 
     dc->fw_name = "PowerPC,POWER7";
     dc->desc = "POWER7";
@@ -8384,6 +8419,7 @@ POWERPC_FAMILY(POWER7)(ObjectClass *oc, void *data)
     pcc->pcr_supported = PCR_COMPAT_2_06 | PCR_COMPAT_2_05;
     pcc->init_proc = init_proc_POWER7;
     pcc->check_pow = check_pow_nocheck;
+    cc->has_work = cpu_has_work_POWER7;
     pcc->insns_flags = PPC_INSNS_BASE | PPC_ISEL | PPC_STRING | PPC_MFTB |
                        PPC_FLOAT | PPC_FLOAT_FSEL | PPC_FLOAT_FRES |
                        PPC_FLOAT_FSQRT | PPC_FLOAT_FRSQRTE |
@@ -8400,7 +8436,8 @@ POWERPC_FAMILY(POWER7)(ObjectClass *oc, void *data)
     pcc->insns_flags2 = PPC2_VSX | PPC2_DFP | PPC2_DBRX | PPC2_ISA205 |
                         PPC2_PERM_ISA206 | PPC2_DIVE_ISA206 |
                         PPC2_ATOMIC_ISA206 | PPC2_FP_CVT_ISA206 |
-                        PPC2_FP_TST_ISA206 | PPC2_FP_CVT_S64;
+                        PPC2_FP_TST_ISA206 | PPC2_FP_CVT_S64 |
+                        PPC2_PM_ISA206;
     pcc->msr_mask = (1ull << MSR_SF) |
                     (1ull << MSR_VR) |
                     (1ull << MSR_VSX) |
@@ -8453,10 +8490,53 @@ static bool ppc_pvr_match_power8(PowerPCCPUClass *pcc, uint32_t pvr)
     return false;
 }
 
+static bool cpu_has_work_POWER8(CPUState *cs)
+{
+    PowerPCCPU *cpu = POWERPC_CPU(cs);
+    CPUPPCState *env = &cpu->env;
+
+    if (cs->halted) {
+        if (!(cs->interrupt_request & CPU_INTERRUPT_HARD)) {
+            return false;
+        }
+        if ((env->pending_interrupts & (1u << PPC_INTERRUPT_EXT)) &&
+            (env->spr[SPR_LPCR] & LPCR_P8_PECE2)) {
+            return true;
+        }
+        if ((env->pending_interrupts & (1u << PPC_INTERRUPT_DECR)) &&
+            (env->spr[SPR_LPCR] & LPCR_P8_PECE3)) {
+            return true;
+        }
+        if ((env->pending_interrupts & (1u << PPC_INTERRUPT_MCK)) &&
+            (env->spr[SPR_LPCR] & LPCR_P8_PECE4)) {
+            return true;
+        }
+        if ((env->pending_interrupts & (1u << PPC_INTERRUPT_HMI)) &&
+            (env->spr[SPR_LPCR] & LPCR_P8_PECE4)) {
+            return true;
+        }
+        if ((env->pending_interrupts & (1u << PPC_INTERRUPT_DOORBELL)) &&
+            (env->spr[SPR_LPCR] & LPCR_P8_PECE0)) {
+            return true;
+        }
+        if ((env->pending_interrupts & (1u << PPC_INTERRUPT_HDOORBELL)) &&
+            (env->spr[SPR_LPCR] & LPCR_P8_PECE1)) {
+            return true;
+        }
+        if (env->pending_interrupts & (1u << PPC_INTERRUPT_RESET)) {
+            return true;
+        }
+        return false;
+    } else {
+        return msr_ee && (cs->interrupt_request & CPU_INTERRUPT_HARD);
+    }
+}
+
 POWERPC_FAMILY(POWER8)(ObjectClass *oc, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(oc);
     PowerPCCPUClass *pcc = POWERPC_CPU_CLASS(oc);
+    CPUClass *cc = CPU_CLASS(oc);
 
     dc->fw_name = "PowerPC,POWER8";
     dc->desc = "POWER8";
@@ -8466,6 +8546,7 @@ POWERPC_FAMILY(POWER8)(ObjectClass *oc, void *data)
     pcc->pcr_supported = PCR_COMPAT_2_07 | PCR_COMPAT_2_06 | PCR_COMPAT_2_05;
     pcc->init_proc = init_proc_POWER8;
     pcc->check_pow = check_pow_nocheck;
+    cc->has_work = cpu_has_work_POWER8;
     pcc->insns_flags = PPC_INSNS_BASE | PPC_ISEL | PPC_STRING | PPC_MFTB |
                        PPC_FLOAT | PPC_FLOAT_FSEL | PPC_FLOAT_FRES |
                        PPC_FLOAT_FSQRT | PPC_FLOAT_FRSQRTE |
@@ -8485,7 +8566,7 @@ POWERPC_FAMILY(POWER8)(ObjectClass *oc, void *data)
                         PPC2_FP_TST_ISA206 | PPC2_BCTAR_ISA207 |
                         PPC2_LSQ_ISA207 | PPC2_ALTIVEC_207 |
                         PPC2_ISA205 | PPC2_ISA207S | PPC2_FP_CVT_S64 |
-                        PPC2_TM;
+                        PPC2_TM | PPC2_PM_ISA206;
     pcc->msr_mask = (1ull << MSR_SF) |
                     (1ull << MSR_SHV) |
                     (1ull << MSR_TM) |
@@ -8544,6 +8625,13 @@ void cpu_ppc_set_papr(PowerPCCPU *cpu)
     lpcr->default_value &= ~(LPCR_VPM0 | LPCR_VPM1 | LPCR_ISL | LPCR_KBV);
     lpcr->default_value |= LPCR_LPES0 | LPCR_LPES1;
 
+    /* P7 and P8 has slightly different PECE bits, mostly because P8 adds
+     * bit 47 and 48 which are reserved on P7. Here we set them all, which
+     * will work as expected for both implementations
+     */
+    lpcr->default_value |= LPCR_P8_PECE0 | LPCR_P8_PECE1 | LPCR_P8_PECE2 |
+                           LPCR_P8_PECE3 | LPCR_P8_PECE4;
+
     /* We should be followed by a CPU reset but update the active value
      * just in case...
      */
-- 
2.1.4

      parent reply	other threads:[~2016-06-21 21:50 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-21 21:48 [Qemu-devel] [PATCH v2 00/10] rework exception model to support the HV mode Cédric Le Goater
2016-06-21 21:48 ` [Qemu-devel] [PATCH v2 01/10] ppc: Fix rfi/rfid/hrfi/... emulation Cédric Le Goater
2016-06-22  2:46   ` David Gibson
2016-06-22  6:48     ` Cédric Le Goater
2016-06-23  5:50       ` David Gibson
2016-06-23  6:08         ` Cédric Le Goater
2016-06-23  6:14           ` David Gibson
2016-07-15 15:17             ` [Qemu-devel] [Qemu-ppc] " Mark Cave-Ayland
2016-09-05 20:25         ` [Qemu-devel] " Thomas Huth
2016-09-05 20:30           ` Cédric Le Goater
2016-09-05 20:51             ` Mark Cave-Ayland
2016-09-06  0:16               ` David Gibson
2016-09-06  7:07                 ` Mark Cave-Ayland
2016-09-07 10:50                   ` Cédric Le Goater
2016-09-07 11:08                     ` Benjamin Herrenschmidt
2016-09-07 12:13                       ` Cédric Le Goater
2016-09-07 21:48                         ` Benjamin Herrenschmidt
2016-09-08  6:59                           ` Cédric Le Goater
2016-06-21 21:48 ` [Qemu-devel] [PATCH v2 02/10] ppc: define a default LPCR value Cédric Le Goater
2016-06-21 21:48 ` [Qemu-devel] [PATCH v2 03/10] ppc: fix exception model for HV mode Cédric Le Goater
2016-06-22  6:27   ` David Gibson
2016-06-21 21:48 ` [Qemu-devel] [PATCH v2 04/10] ppc: Fix POWER7 and POWER8 exception definitions Cédric Le Goater
2016-06-21 21:48 ` [Qemu-devel] [PATCH v2 05/10] ppc: Fix generation if ISI/DSI vs. HV mode Cédric Le Goater
2016-06-21 21:48 ` [Qemu-devel] [PATCH v2 06/10] ppc: Rework generation of priv and inval interrupts Cédric Le Goater
2016-06-22  6:51   ` David Gibson
2016-06-21 21:48 ` [Qemu-devel] [PATCH v2 07/10] ppc: Add real mode CI load/store instructions for P7 and P8 Cédric Le Goater
2016-06-21 21:48 ` [Qemu-devel] [PATCH v2 08/10] ppc: Turn a bunch of booleans from int to bool Cédric Le Goater
2016-06-21 21:48 ` [Qemu-devel] [PATCH v2 09/10] ppc: Move exception generation code out of line Cédric Le Goater
2016-06-22  6:57   ` David Gibson
2016-06-21 21:48 ` Cédric Le Goater [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=1466545735-2555-11-git-send-email-clg@kaod.org \
    --to=clg@kaod.org \
    --cc=agraf@suse.de \
    --cc=benh@kernel.crashing.org \
    --cc=david@gibson.dropbear.id.au \
    --cc=qemu-devel@nongnu.org \
    --cc=qemu-ppc@nongnu.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).